@Iamnotausername I have a lot of pax wardrobes in the bedrooms but also a 4m wall of them in the children's playroom meaning I have assembled a lot of them.
I think the oak doors look decent, my children have the white oak doors. Re drawers, the best thing about internal drawers is you can space them out height wise meaning you can overfill them which you will never be able to do with a chest of drawers. Are you having double wardrobes, singles or a combination?
I assume you are having hinged doors, you cannot put a wooden drawer at the very bottom of the wardrobe due to the metal runner allowing the drawer to be pulled out also being at the bottom of the drawer. The hinges for the doors use the bottom holes. Your possible solutions are put a metal pull out basket at the bottom as the metal basket runners are at the top of the basket or you leave a gap at the bottom under the wooden drawers. Bear this in mind for where the middle hinges go too for shelves. The mirrored doors are very heavy. Unless you only have a hanging rail inside then an internal mirror would be difficult to fit in due to the possibility of the internal shelves etc touching the mirror on the door.
Re space, have a look at videos on YouTube lots show them being put together and upright too. I have literally laid some across my bed rather than on the floor to put some together. You can always make them in another room but be aware of height and tipping them under door frames. Putting them together upright is more difficult as you have nothing to push against whereas if you do it on the floor or bed you at least have something relatively solid underneath.
If you know what internal fittings you are having, attach the runners or shelf supports to the side panels before you put it together, just makes it easier. If they are going on a carpet floor those adjustable feet at the front will come in handy as the wardrobe will sit on the carpet gripper making it slightly higher at the back. We screw the wardrobes together, not with the connecting bolts but just a long screw that goes through one wardrobe side panel and half way through the other one. A pair of clamps or another pair of hands is helpful for lining them up to do this, also a spirit level. And attach them to the wall for safety. Any more questions, just ask.