I see you got your answer, but I’m adding on for anyone else that comes across this.
For me, I learned the most when I had a disposable and replaceable system. When I was dual booted I was too scared to touch anything in case it fucked everything up. Once I started poking round on a Pi, LiveUSB, etc it was a lot easier to learn because I could always restart.
Id start there with something like Mint or Ubuntu. Then set it up in a way where you can easily replace your OS so you can reset it often and fuck around. Then just learn as you go.
Desktop for sure. Though I’ve started to love using Steam Link in my home to stream to my laptop (or TV) to get the best of both worlds.
Same reasons as everyone else, it’s more powerful, better heat management, upgradeable, and still allows me to stream to a laptop when needed. (I’ll even use RDP to my desktop from my laptop most of the time to still get the power for work things too).