So, there's an install button in the GOG Galaxy client for BG3.

the question is, which version will it install if I click it now.

This "Install"-Button was allways there since EA...By Clicking on "Install", a Dialog opens, where you can see the size of the installed package (topmost of Dialog-Window), if this is below around 100GByte (69Gbyte Download/ 79Gbyte installed), it is still the EA-Version...

The Install Pic is a new one now but still EA download size.

Cheers.

Seems to me that Galaxy could use some improvements in UX.

If you click install you see the total size of Early Access is 69 GB.

When the full game is released, expect it to be more like 120GB.

It really is quite terrible that there is absolutely no indication on the product page that you'll be installing a useless version, this close to the final release.

Those coming from Steam are used to pre-download and then the game just unlocking at release and could get tricked by this.

Yeah, it would be helpful to see the button disabled or to show the version you are installing - I saw that the button was enabled and kicked it and saw the EA "size" - it did download it to see what happens (supposedly the EA version should be unavailable), it only partially downloaded before the install showed a "failed" - I just had to try and see ;-).
So, like mentioned not ideal UI handling and also unnecessary traffic.

Now the "In development" tag got removed, but the install download is still just 69GB..

Yeah still EA.

It's released on Steam now.

https://store.steampowered.com/news/app/1086940/view/3655285941431060622?l=english

Restart gog Galaxy, it's downloading for me with the correct size.

Nope, still 69GB

Yep - The off-line install files also still say EA...

On Steam downloading has already started looking at the comments.

For me it's saying 106 GB.

105.45 GB for me, looks like it's up. Offline installers says will take 1-2h more to appear.