Competition is good.
At present Bg3 is prettier and Solasta has the better interpretation of the rules. Hopefully the end result will be a Solasta that's more BG3 like and BG3 that's more Solasta like.
In addition, each game should have their priorities, and be good at meeting those. Interestingly, back in the days, Baldur's Gate had the better story and roleplay. Icewind Dale was the better dungeon crawler. There isn't a one-to-one correspondance with Baldur's Gate 3 and Solasta today, but both games don't aim for the same goal.
They don't exactly have equivalent positions though.
I don't think Tactical Adventures can do much to make Solasta prettier, given the constraints of a smaller team and smaller budget. I suppose that things like dialogues, avoiding combat, and perhaps multiple resolutions for quests (and possible permutations) are more within reach though. Larian Studios has a much bigger capacity, and the good ideas they could perhaps take from Solasta are not the more expensive ones, like video quality, but the cheaper ones, like adapting the 5E rules in video game form, etc. I'm giving these examples without having tried Solasta, it's more generic/theoretical examples.
So Larian has the better means to act on the good ideas of Tactical Adventures. But regardless, it is true that each studio can reap some benefits from the other having EA at the same time. Basically, they can gather feedback on some ideas without having to code them, provided that the other studio is trying them out.
I don't know if the fact that the audience is likely to overlap strongly is a helping factor. But I hope that most devs on both studios are playing the EA of the other on their work hours.