I will go it point by point as far as I can.
From what I've seen, the only real comparison is that you travel on a world map rather then navigate the world on-foot. In blackguards your destination could be a number of areas, from combat screens to NPC homes to town squares, but it seems like Druidstone is always either your start point or a combat screen? To which the only other comparison is that the combat screen is then contained within it's own individual chess-board and takes place in a turn-based system.
Yeah, both games are pretty linear with some occasional choice of "which mission to do next". And missions always consist of combats which are quite puzzle like.
I wouldn't describe Blackgards destinations as missions, more often than not you're just encountering a monster, the same as you would in any RPG, to which you are free to deal with that monster however your build prefers, in as many turns as you like. In Druidstone all scenarios are essentially puzzles with a specific objective beyond 'kill all enemies' are they not? While Blackguards may spice things up with the occassional combat scenario which is a bit puzzly, in Druidstone it's always puzzly, yes?
Blackguards was also always puzzly on higher difficulty. And if you happen to chose the wrong skills it might become plain impossible. In addition you had a huge bunch of randomness (due to having the Dark Eye as Basis which is fine, but not in that invironment). I played both games on hard. Of course the easier you make it, and the less you focus on bonus objective (I remember one mission in Blackguards where rescuing a person was a "bonus objective") the less "puzzly" it becomes.
The maps in Druidstone are a bit bigger than in Blackguards, which makes it a bit less puzzly on that end.
Besides of the missions with battles you also have some ingame cutscenes which you can start as missions themselves. First time you start the battle however you first get the "story"-part then the "battle"-part and then again the "story"-part for example. After you completed all you can rewatch the storyparts or try to get a better restults in the battles.
As a third kind of map (only saw one of these yet) there is also pure puzzle maps without fights, which give you an additional bonus (a gem you can use to enhance your abilities).
And when Blackguards is occasionally puzzly, it is doing so because one of it's unique selling points was the concept of "manipulation of the environment", ie: you could set a table on fire and the skeleton would stand on the fire while attacking you, providing extra damage, something that was entirely optional and just 'cool'.
On hard difficulty and when trying to get optional goals this was not optional and you needed to add this into your solution of the puzzle.
I'm not seeing any environmental aspects to Druidstone with regards to the puzzles, to which the example of respawns makes evident: In the rare times Blackguards had respawns in a scenario you could close-up the holes that generated the respawns, Druidstone seems to have no similar option and more than that uses respawns in every (?) encounter regardless of creature type or sense of realism.
I don't even remember respawns in Blackguards anymore. In fact I would have prefered that, as I dragged some combats far longer than they were enjoyable in order to heal within them. As in combat in Blackguards you could regenerate mana, and with mana you could heal. Out of combat you needed to pay gold to heal.
That said, Blackguards also has environmental elements. I just finished a map where I had some dynamite where I tried to gather enemies around to have them explore. In a previous there was something similar with an ice crystal. These are more straight forward than in Blackguards though, which is also a good thing as in Blackguards you needed to do a test run first in order to see which tiles are affected by the trigger.
Even the words used in describing the scenarios is different, in Blackguards you complete quests, whereas in Druidstone you complete missions hence: in Blackguards you can never re-do a scenario once completed whereas in Druidstone you can re-do scenarios as much as you like?
Yep, you can redo them as often as you like which is different.
Blackguards has a massive character creation and build system [you call "very bloated" which I find to be a very unfair and inaccurate description] combined with a level-up system which put the focus of player-interest in the development of their characters, whereas Druidstone has no character creation and a very basic level-upping system.
Blackguards just took the Dark Eye system and somehow tried to squeeze it into this tactics game without adjusting it a lot to the different type of game.
As far as I remember Blackguards also only had a character generation for your main character. Blackguards offered much more options when doing a level up, but in this surrounding not a lot more of useful choices (at least on higher difficulties). A good chance to gimp your character.
The stroy of Blackguards took up quite a lot of screen time, either in dialogues, cut-scenes or following up on leads, where as Druidstone is much more just looking for an excuse to do another puzzle-mission, no?
I found the scenario of Blackguards more interesting than in druidstone as well. But that's because I like these down-to-eath Dark Eye stories.
However I am actually quite surprised on how much story (in form of these ingame cutscenes) you can find in druid stone. I'd say that there is quite a lot of story and it's not bad either.
And from your first quote, Blackguards has randomness (dice, to-hit etc) where as Druidstone doesn't (deterministic), again an important difference in 'RPGness' design. I also just disagree that Backguards is either unpolished or has bad mechanics, it always stuck me as a very polished game with both interesting and unique mechanics, but you're referring to Druidstone as polished when other people are saying a lot of the unpleasant elements of it's puzzle scenarios come from unpolished AI design and the like; AKA cheap tricks, and Blackguards never needed to use cheap tricks.
This is a bit unspecitic. But related to the "cheap tricks" I'd also say that Blackguards often broke because it didn't use them. E.g. the before mentioned kiting and in-combat-healing. Regarding randomness in Blackguards: There were missions/quests where you basically could only win (depending on your setup) when you first succeeded with a spell, which had a 45% chance to work. And after that almost none of your 90% hit chance hits must miss. So it was a massive chore of reloading.
But to summarize why I compare these games:
-They are both semi-linear games where you chose which battle you do next
-Both feature turn based combat with very puzzle like gameplay
-Both give you pre designed characters (besides of the main char which you can set yourself in Blackguards)
Other games you could compare Druidstone with are:
-Tahira, but Tahira has less storey and no character development at all. In fact Tahira as hardly any RPG elements at all. Don't get me wrong: Tahira is awesome.
-Halfway (the predecessor of Pathway), which had less puzzly fights and also an evem simpler character system
Some of the "fun" moments in blackguards can also be found in my "review" from 4 years ago, which was really more of an opinion piece. Blackguards is one of the few games which I aborted half way through it. Not one of my best reviews either, but I guess it got the essentials.
Scene from 1:50 to 2:10: of the beforementioned randomness (and this mission also had the time limit)
Scene from 2:15-3:00: which is the mechanic to "heal yourself" by regenerating mana as described before and kiting opponents.
Scene from 4:38 - End: Using the lack of time limitation and stupid AI to maximize benefits, e.g. not getting hit and healing.