Game is slightly different which I guess is good? My toon talks to much for one. The turn-based mecs are worse than before. Like I can only move but not cast a spell? The little brian that follows you around the ships is useless. I have played up to the battle at the Druid fort entrance so far with this new download. Before that I just stopped playing for about a few weeks. Back now, but not sure I will keep playing if the mecs do not get fixed to work more fluidly and work?
Your toon talks too much because there is now a default setting that you can adjust to your liking. Go to settings. Adjust the frequency of your character talking to Never or close to never. Then they won't talk so much.
I'm not sure why you are saying you can't move and cast spells. Any spellcaster in BG3 should be able to move and cast a spell. Maybe you are using the Dash Action too much. You can only do 1 Action per turn - either a spell or attack with weapon or Dash, etc. To be clear, moving is free up to 30 feet (about 8 meters). After that, if you use Dash Action, you can go up to 60 feet (16ish meters). You don't need to hit an Action button to move. Just move for free. Then you can use your Action for something else.
Also, you can't attack with weapon and cast spell and Dash all in 1 turn. Just 1 Action. Either you use your weapon or a spell. That's D&D 5e rules which BG3 is using D&D 5e rules.
Not sure why Us, the brain, is useless to you. He's actually a very powerful minion in the prologue. Maybe you aren't bringing him into battles? Or maybe you are using Dash instead of attacking?
I don't know. I don't want to sound harsh, but it really sounds like you are just not understanding the rules of the game. You might need to read the Tooltips more. If you are expecting DOS 2 combat, this is not DOS 2 combat. You don't get like 6 action points to spend. You get only 1. You then also only get 1 Bonus action to do only select things.
My point is, I don't think there is too much wrong with the mecs. It sounds more like a user error - maybe just not understanding the rules of the game. Either that or there is definitely something wrong with your download.