bzLem0n

No real advice but I’ve heard of people having issues with their BTRFS filesystem running out of free inodes and reporting the filesystem as full due to that. Note that the df command is not expected to work properly for a BTRFS filesystem.

1. Linux Mint Debian Edition if you must use Mint and stick with KDE plasma desktop on whichever distro. I’d recommend avoiding ubuntu and Manjaro.
2. Xournal++ is the only one for this purpose I’ve heard recommended. I use Zim for what I need.
3. It’s going to be slow and will wear out the SD card eventually but it deserves consideration. I strongly recommend keeping the already installed Windows and using a SD card or USB C drive for Linux, particularly if you’re still intending to actively use it for note taking. You could use a USB C device like a NVMe enclosure or something that supports UAS and get good speed on the Linux install if the Surface supports UAS.
4. Nothing to offer.
5. Make sure your backups of anything you don’t want to lose on the Surface are up to date before you start anything. Linux installers will normally prefer an internal disk so if you forget to change that when installing all those files will be gone.

Snapdragon is an ARM CPU which means if you can find a distro to run on it, it’ll likely be an Android custom ROM, whereas Celeron is x86 and should run most Linux distros without issue.

I have a system with a Ryzen 1700 with the same issue and have found the only reliable way to run it is by installing and enabling the disable-c6-systemd package from the AUR. The other fixes provided in the wiki article you linked are correct but aren’t sufficient on my system, the CPU keeps reenabling the C6 state on its own and the disable-c6-systemd package works to counter that. The reason it works on Windows is they’ve disabled the C6 state by default for the CPU.