Definitely check out Ventoy.

You can boot into a Linux distro on a USB stick and use GParted to create as many partitions as you like. Mine are mostly ext4, I believe, but I don't know if they need to be.

Having a partition for each distro separate from your files makes updates easier, and you can reinstall things if you mess them up.

I'd keep the existing boot partition, I think, but you could replace it. I kept Windows and added 4 distros beside it, for different sets of tasks.

If it's EFI boot, you can check out rodsbooks.com/rEFInd, nice for booting into different distros.

There are a few tricks to it. If you install multiple related distros ( like variations on Ubuntu), they may overwrite the boot folder from the last one, if you don't go in and rename the existing ones first. I found Linux Mint handiest for getting into the system files to set those things up - it allowed me access where others didn't, so installing it first worked nicely.

Have fun. If you have different use cases in mind, Ventoy makes it easy to try a bunch and see what works best for each purpose.