It wouldn’t be the most ideal, but you can dual-boot with an external drive. There are external SSDs that are meant for running programs/games off of them, and would look into those for best performance.
Alternatively, if you have plenty of unused storage on the laptop you can partition some of that for use, but a second drive is usually preferred.
In theory you should be able to do that! I think Proton has some issues with NTFS, mostly when installing or updating, but with a little research and tweaking you should be able to get it to run smoothly. I opted to keep them fully separate and just installed certain games twice, but am also using this as a test run before diving into full daily driver Linux when I build a new system in the spring, so longevity of my storage drives wasn’t a concern.
Some cats do like it! Depending on situation, mine do as well, but my roommates have a cat who will quickly flop over to show her belly if you pet her, but will act offended and give a warning bite if you try to pet her there