If you have the option to use separate drives, then always do so even for Windows + Linux, much less two Windows. That way each OS only ever sees its own boot manager so you don't have to worry about reinstallations messing up both installs.
Unfortunately compatibility with both Win 7 and Win 11 implies an 8 year old laptop, by which time easy-to-swap slide-in drive sleds were no longer a thing, but if you have say both a NVMe and a SATA drive in the laptop, you could leave them both in and select which one to boot from in the BIOS.
I will suggest to install each Windows with only one drive attached, so the dumb installer doesn't put the boot partition on the wrong drive. But after both Windows are installed, you can leave both attached. I would disable the autochk chkdsk for a dirty bit set on the Win 11 drive in Win 7 so it doesn't corrupt your 11 filesystem.
The other option is to install 7 on a VM in 11, which should work on even a much newer laptop.