Persistent Live USB/Installing 3rd party packages and GPU drivers

I have a work laptop that has CentOS 7 installed. I can’t change that, i.e. I can’t install Rocky to dual boot, or update to Rocky 8 or 9. I do however want to have Rocky 8 and 9 available on this laptop. What I want to try is install Rocky on a USB drive and boot from that. I know I can do that with persistent live usb install, which gives me persistent storage, but I need to install additional 3rd party packages and GPU drivers. Is this possible? If so, what is the best approach?

In theory you can do a normal installation using cd/dvd and set the usb drive as destination during install. Than you can set you bios boot order to boot from usb drive first than from hdd.

So you can boot usb drive if connected and if not connected you drive from hdd.