Yes it uses 5th Edition D&D that is pretty much the only hard fact we have about the gameplay at the moment. The good thing is that there are currently at least 4 larger DND RPG in development so even if BH3 won't make everyone happy there are others. Though BG3 is the only one of those made by a studio with over 20 years of experience and a non-indie budget. BG3 will most likely be the one where people with no previous DnD experience will still be able to learn the system without being overwhelmed.
It's important to be clear and precise as to not breed misinterpretations and false expectations.
The initial starting point was the Player Handbook. Then to fit a video game medium, they've needed to take some creative liberations and choices to implement systems that for example removes the game master. So if you're expecting a 100% 5e to video game D&D experience, so I believe it's fair to recommend keeping a certain healthy dose of insight in what it takes to derive from one type of medium into another, even when the style itself is inherently similar in many ways. So some creative decisions and interpretations how to make something work for a video game while trying to stay true to what it's derived from in essence is inevitable. Some fans will misinterpret and/or be disappointed by how their expectations misalign with this reality.
