Mac Pro 5,1 to Sequoia?

Please bear with me. I used to be pretty tech savvy but as I've got older (now in my mid 60s) I'm losing pace with things a little. I've looked at the OCLP pages many times, but I'm a bit out of my depth these days.

I have a 2009 Mac Pro, upgraded to 5,1 firmware & with dual 3.46GHz Xeons & a Metal 2 GPU, AMD HD 7950, currently running Mojave.
Is it possible to jump this all the way to Sequoia in one 'easy' step, with no hardware changes? I don't have the money for another GPU upgrade.
I have 6 drives in here. If I take out all but one & work to that, is everything else 'safe'? Can I revert to the previous OS by swapping the drives back? If yes, is this something I can also do with both OS drives in place, with a startup manager of some sort?

I have access to other Macs (Intel & Apple Silicon) to help with downloads & other online access whilst I'm attempting this, but this is my main workhorse Mac so I'm keen to do it with as little down time as possible.