If it’s (really) just a bit than it’s ok.
Twistbones have to be painted manually (as they are child bones that are in line with their parents). Automatic weights would not work in that case. But you could copy the vertex groups (e.g. upperarm_l and rename it to upperarm_twist_01_l) and afterwards subtract from both vertex groups some weight with autonormalizing on (so you get 1.0 weight). This works if you use the weightpainting from Makehuman (not sure how this would look if you use that automatic weights). The next version of the ManuelBastioniLab should include some twist bones already (which is pretty cool).
You could even use high-poly eyes (it’s a nice base if you would create some more advanced eye with cornea and iris hole). But I would recommend to switch either of those with some mesh from UE4 (content example - eye shader demo - export mesh, import into blender, and replace with the eyes from the Makehuman export).
You could even include hair and eyebrows and cloth. They all got proper weightpainting from Makehuman. Usually I would even recommend to use the skeletal mesh from Makehuman (and just change the rest-pose instead of replacing it with some other rig).
Yep.
Maybe. I never used this rig for UE4 (neither for makehuman, manuelbastioniLab or my own meshes). But if I would use it I’m not sure if deleting the layer2 would be a good idea. Probably just once to get your automatic weights (if you go this route). However you would even have to add at least the twist bones back again afterwards.
Sounds good if you don’t have cloth with weights already and/or if you created your own cloth in Blender.
Yep.