I would like to address an issue that I know is fairly polarizing. Some time ago RPGs and combat simulation games started this thing of scabbards on the back of the characters (It seems like the Witcher series also had a big part in this). I was really disappointed to see the same thing being implemented in BG3. Now, here is were personal preference comes in. If you think it looks cool and BG3 needs this to compete with other titles...well, this whole point is moot. However, if you are interested in realism (or maybe I should say believability in a context of a fantasy RPG), please read on.
So here are my premises:
BG3 is trying to achieve a certain believability/credibility factor when dealing with (non-magical) weapons.
BG3, being based on DnD 5e, is modeling weapons taken from Historical European Martial Arts (HEMA).
If you agree with these premises, here are my arguments:
1. Historical accuracy: As far as we know (and by "we" I mean historians and HEMA experts), nobody has put weapons on their back in medieval times. Scabbards for swords, short swords, and daggers were always attached to the belt in some form or fashion. Zweihander (in game called a "great sword") were just carried and usually not sheathed. However, there is discussion out there about that, but if you approach it with common sense, it should be obvious why. An that brings me to the next point...
2. Practicality: If you ever get a chance to handle a sword, try it. Put it on your back and unsheathe. If the sword is longer than your arm, it's simply impossible (I think anybody can imagine that, even without the experiment). So, long swords are out by default. Let's say with have a sword which is shorter than your arm's length, a short sword like the Gladius, or a long dagger. Drawing it, would not be a big problem, but then, try to sheath it. Believe me, it isn't easy. And my follow up question would be: Why is it on your back in the first place when it's short? Isn't it more practical at your hip, where you can reach it easier and quicker(!) than reaching for it on your back? Besides, someone might sneak up on you and just draw it for you.
In the case of long swords: You could still sheath a sword and THEN put in on your back, or take it of your back and draw it. But why would you do that? Apart from having the sword out of your immediate reach and sight, and not being able to draw it readily, you can't sit down with that thing on your back, and it is likely to get stuck entering through a low doorway, passing under branches, etc., simply because it is out of your own sight. Again, try it at home: Attach a broomstick or something like that on your back and go hiking in the woods with it...depending on your body length, you might not even make it out of the door.
In terms of believability, all other weapons are even worse... how do you wear a war hammer, a battle axe, or a quarter staff on your back? How do you attach it? And if you somehow manage to do so, is it ready to be drawn quickly? If you went through the broomstick experiment mentioned earlier, I'm sure you already see my point here.
Sure, in the case someone capable of magic, the weapon might be just attached magically, and more or less just hover there. But then, why would it not hover next to the wielder, being less of a nuisance?
3. If you are still not convinced, don't take my word for it, listen to a historical expert and a HEMA instructor who talks about this subject in this video: https://youtu.be/UKAbw69Mh3g
He is talking about other games and his suggestions are maybe not entirely applicable to BG3, but he makes a few very good points.
And as a final argument, specific to BG3: In BG2 the characters had their weapons in their hands and it looked really good and credible imho.
So, please, dear developers, consider this and make this game stand out from pack of unrealistic and sometimes ridiculous depictions of weapons and HEMA fighting. After all, this is not Final Fantasy, or something along these lines. So how about having each weapon carried in a way that makes historical and practical sense.
As is, there is an option to unsheathe and hold weapons at the ready by pressing TAB. A quick temporary solution might be to add a "realism" check box where weapons would not be on backs by default or...if the community agrees, maybe remove this Final Fantasy stuff altogether?
Other than that, dear developers, keep up the great work creating an epic game that is coming along splendidly!