Your best bet here is to use tiling textures, rather than trying to uniquely unwrap each piece - especially for things like walls. You can use smaller bespoke parts to break up repetition, mixed with with maybe something like a vertex colour blended shader and decals.
You have to care about texel density only if your shader does another macro or micro texture layer scaled of same UV. And of course for same materials sharing same textures. Having those edge blocks a bit higher res is nothing wrong at all. For distant background buildings out of close player access it would be a rule…