do GSI roms still contain google binaries (play store, play services, etc...) or is it similar to a AOSP rom where its just a bare android image
Yes. That's to say they can be either depending on how the ROM was built. All of the GSI ROM builders I've worked with usually have multiple releases of the same build with different configurations: root, no root, with Google services (often MicroG), without Google services, combinations of both, etc.
To my understanding, GSI ROMs are basically just the "userland" portion of a full ROM. Basically they use the stock/existing kernel, drivers, etc but replace the rest of the system that runs on top of it. If memory serves, they're possible due to Project Treble. Sadly, they still require an unlocked bootloader to install, so they're not a total fix-all.
They're also very generic generic images (hence the "G" in the term). They're not optimized for any specific device and can be hit-or-miss feature wise depending on the device. If you're already reading about a specific device on XDA forums, then you'll probably be able to see what works and what doesn't.
TL;DR: Running a GSI ROM is like upgrading to a newer Linux distro but without upgrading the kernel.

Ugh. Just stop with all the "infotainment" nonsense and give us the aux port back.