I’d say that it depends on your workflow if you use bsp for prototyping or if you design everything on paper first.
As long as you are building everything on scale, you might not even need to launch UE4 till your models are ready for import.
Finding the right scale is the issue for some ppl.
Often it’s better to see the size of a room in the engine to determine if it’s right or wrong.
Since 1UE=1cm in C4D, it’s not that hard to nail down the messurements though.
As for texturing, you need to know how to use UV edit in C4D, since realtime engines only accept UV mapping.
Still you can apply your Materials in C4D with other Projection methods such as cubic or cylinder,
but you need to bake them to your UV mapped layout to get usable textures.
I’d recomend the “bake texture”-Tag for that job.