I dont know about the second one, but to your first question in the snaps menu (choose what to snap to) on one of the tabs there is use axis constraint, I think this should solve your issue.
Get benchmarks. Build everything with max quality (2k and 4k textures) in mind, and scale down where necessary. Everything is circumstantial, especially console development, at least you have set hardware constraints.
You can also use one of several object painter scripts like Neil Blevins script. You can also use a attachment constraint to stick objects on meshes and have them follow.
When Select Contiguous Edges stops working, all ya have to do is open Selection Constraints... and hit the Close and Reset button. You can map that function to a hot key for an automagical fix.
You won't be able to bake if you are linking. The baking tools have never supported a parent/child relationship. You will want to use constraints, then bake.