Some software libraries use GM or GM2 but many do not, and if you pay for a good library, you probably won't use GM or GM2 sounds because you'll have better available.

Most hardware synths will support GM and GM2. Some, like my Roland, add better sounds too. You get them in BIAB by using a Patch Map. I can explain more about that (I've written some).

But first -

Have you ever seen PG Music's page on this topic? It really old but it's still a great way to begin. Go here: https://www.pgmusic.com/dare-to-compare.htm Just keep in mind that sounds can be much better now than in these demos.

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