Hi. I don't even have BIAB on my laptop, though many here do and are happy with it. Likewise I have not felt the need for multiple monitors for BIAB though again, many here are happy with them. There are occasional comments how BIAB windows could be managed better on multiple monitors, but I don't know specifics.

A desktop is cheaper for the same power, and upgradable so much more easily. I build all my own desktops, too.

If you are really optimizing for BIAB, then put your money into the CPU and the sound interface, and don't worry as much about the video, or even the RAM unless you use soft synths extensively.

My monitor is a standard 24". I recall a few comments by those with monitors much larger that there are occasional dialog boxes where the text is smaller than they would like, and yet changing the default Windows size larger than 100% causes its own problems.

You'll get tons of differing opinions here, no doubt. Hope this helps a little.

BIAB 2024 Win Audiophile. Software: Studio One 6.5 Pro, Swam horns, Acoustica-7, Notion 6; Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus Studio 192, Presonus Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors