3ds max to UE4 - beginner questions about best workflow

Hello Everyone!
I’m very new to UE4, I’ve just followed the awesome tutorial by Chris Jennings “Creating an Interior Walkthrough in Unreal Engine and 3ds Max”, but now i need some tips from you guys

For example, yesterday i modeled some pieces to build a depot/hangar/warehouse (I don’t know the correct name in English).
This scene is composed by many modular meshes.
Here my doubts:

1: it’s better to import the basic meshes in UE, set their material there and then build the model in unreal duplicating and snapping those meshes, or importing the entire warehouse from 3ds max, or maybe… something else?

2: groups: in 3ds max I use a lot groups, but when I import them in UE4, they are obviously just single meshes… which is the best workflow? Group them in UE4?

3: I just unwrapped everything, to be in space uv1 in channel1… it’s ok somethink like this?

By the way, I just want to ask you how do you guys would approch properly that kind of level design, to work without wasting time and in a clean way!

Hope this thread will be useful also to someone else!
Thanks in advance