Thank you for taking the time to read it  

Ohh yes, I know how ridiculously large the Intuos4/5/Pro (old version) are! Even the Medium size I used to own barely fit into my 15.6-inch laptop bag, so I can imagine how non-portable the Large must be  
Luckily, I have the XP-Pen Star03 and Star05 on hand, and I've been told that the Star06 pen is just an upgraded version (just higher pressure levels) of the Star03 pen, so I'll be using the Star03 pen for the comparison. I also have an old Wacom Bamboo Connect so I can compare all their pens.

I see what your friend means by the balance being top heavy in the Wacom Bamboo pen. The Star03 and Star05 are both less top heavy in comparison, but the Star05 pen has more top-heaviness than the Star03 pen. All these pens actually have their center of balance towards the pen nib, but I can certainly feel the difference in top-heaviness when I pick them up (the Bamboo pen just feels like it has a weight on the top end for some reason). For your friend, I think that the Star06 would have the more comfortable pen of the two XP-Pen tablets.
The weight of the pens, in order of lightest to heaviest is: Star03, Star05, and Wacom Bamboo. I personally don't find that the Star03 pen is too light, but maybe your friend will find it too light and skinny since they're used to the Intuos Pro pen which is pretty wide and heavy due to the rubber grip.

With regards to the lift distance, I don't recall it being so small that I notice it as a problem. The specifications on the product pages for both tablets say that the reading height is 10mm, so I don't think reading height should be a problem.

With regards to the feel of the nib, basically all the alternatives (Parblo excluded) have pen nibs that "sink" quite a bit more than Wacom's. With Wacom, the pen nib barely moves when you apply hard pressure, but with other tablet makers, the pens are fairly springy which gives you a better feel of how much pressure you're actually putting into your stroke. I think it should be around the same feel as if you're using the Wacom nib that has a spring in it. I personally prefer the alternative pens over Wacom's, but that's personal preference, and you can't really decide that until you've tried both for yourself.
One thing to note about pen nibs is that the alternatives only offer the black plastic nibs and don't have other types of nibs. Currently, only Wacom has a variety of different nib types, so keep that in mind if that's an important factor for your friend's art.

About running multiple tablets on the same computer, I think there are some cases where the drivers can both exist at the same time, but you shouldn't get your hopes up about that. There are currently no ways that I know of to have different brand tablet drivers to be installed on the same system without interfering with each other. Maybe you'll find a method if you Google search it, but I recommend against trying to install multiple tablet drivers on the same computer because that's basically asking for the system to mess itself up.
However, your friend could look for a used Wacom Intuos CTL-480 (This one) in their area. It's a discontinued tablet, but it's a fantastic tablet if you can find a used one for less than 60€.
The reason I'm suggesting this is because if it's another compatible Wacom tablet, you don't need to reinstall tablet drivers when switching between tablets since Wacom's driver recognizes all Wacom devices that are connected and treats them separately using the same driver. (Only works for devices that are listed under the "compatible products" list beside Wacom's latest driver here: www.wacom.com/en/support/produ…). Of course, your friend could instead buy a Wacom Intuos CTL-490 series (aka Draw/Art/Photo/Comic) if they're fine with that. I just dislike that series because it looks like a kids toy, costs quite a bit for a small size, and the pen is just a plastic stick (and replacement pens are a whopping 30 USD!)

Something that I think is worth noting for the XP-Pen Star05 is that the wireless is pretty laggy. I have a Huion Inspiroy Q11K which has wireless as well, and I can't tell the difference between when I'm drawing wired or wireless because the wireless is so seamless, but with the XP-Pen Star05, I could clearly see the lines becoming more choppy while I was using the tablet in wireless mode. Of course, this is only something that affects you if you use the wireless, but I figure it's worth mentioning.

Another tablet that I think might be worth looking at is the new Huion H640P and H950P. I don't have them listed on this list because, well, I haven't updated this list in a while (whoops, sorry!). They're also very new so there aren't very many reviews for them yet. I actually have the H640P and there's a little pen pressure blip that I'm consulting Huion about right now, but it's not something that you can even notice while drawing so the tablet is still well worth considering. The pen is also very nice with a fairly wide rubber grip and front-heaviness. I talk about the pen pressure blip in my review if you're interested here.

No problem for all the questions, I'm actually quite happy talking about tablets so ask away~