ranged combat mechanics?

Does anybody know how exactly ranged combat works? Does one get boni or mali for different ranges?
Do you get a disadvantage to shooting when the character is engaged in melee but still uses a ranged weapon?

No and no, sorta.

Wood Elf should technically get a bonus to accuracy when shooting from range (4+ meters) with their racial bonus and Marksman does something similar for everyone (and it stack).

For disadvantages, your ranged character is going to get interrupted (ranged weapons are already quite slow) and have less deflection than melee. Rangers have a talents to gain a deflection bonus if they have a ranged weapon in melee though.

I don't have a single archer in my group, and never intend to. I can tell you from a melee perspective that anyone shooting an arrow at my team gets one shot at most….then they get got. Once my rogue gets to them, she interrupts them so much that the only thing they are concerned about is living….which ain't for long.