While I realize that we're going off of far more limited information that Larian, being as you raised a point, I merely wanted to continue a line of discussion along that point.
I don't like the "number of slots" management personally. Weight management I would be fine with. Slot management leads to either inventory Tetris (NWN / Diablo) or the ridiculousness of an Ankheg Carapace using the same space as 1 potion (BG). It also means that it is more likely that you are given a Bag of Holding earlier (or potion bag, or scroll case, etc) and that just eliminates both styles of management.
Again, I think that it sounds more reasonable in previous editions due to the way that carry capacity scaled off of Strength.
Example from BG: 11 Str = 70 lbs, 15 Str = 120 lbs, 19 Str = 500 lbs, 20 Str =600 lbs
Example from NWN: 11 Str = 115 lbs, 15 Str = 200 lbs, 19 Str = 350 lbs, 20 Str = 400 lbs (These are maximum carry capacities in 3.X, but became the base value in NWN)
Example from 5e: 11 Str = 55 lbs, 15 Str = 75 lbs, 19 Str = 95 lbs, 20 Str = 100 lbs (These are the base values for 5e, the maximum values are 3x. From the Gameplay reveal, you can see that Astarion has 12 Strength and a 60 carry capacity and that lines up with the base 5e loads).
Edit: Timestamp of the inventory. Str is on the 3rd panel, weight below the 2nd.
https://youtu.be/XJhawYZwvPI?t=3028You're right about slots management. The Tetris thing is really boring and the Ankheg carapace is not so realistic (It's like that in many games, DoS included).
I like the way they did it in BG1&2 because it is, according to me a good mix between weight and inventory slots management. A good mix between fun and "realistic"/immersive feelings. A good mix between video games and what is humanly possible to carry.
Don't forget that all characters have a bag of 16 slots, but also weapons slots (in their belt or their back), ammo slots, their bodies as slots,...
Everything looks more "true".
Even if inventory management is sometimes very slow/heavy in BG, I never had to choose between an item or another because I don't have enough slots.
Of course I'm not saying it has to be the exact same. Everything can be improved. It's all about balance and what you want the game looks like.
I talked about KDC earlier and it's only about weight. This is good too but I really don't like those inventory in which you have hundreds of (useless) items on your bags.
In games in which you have unlimited slots players pick nearly everything they can because "it could be usefull" and the results is exactly the same :
=> You have too many things and you have to sort/throw/sell/put in a "bank" or something/...
The only difference is that you CAN forget it, what I'm nearly sure no one does because players like to have "proper" inventory.
Is that really better ? I don't think so...