This is the sensible thing to do. Try a bunch of distros using either USB or as Virtual Machines.
It’ll save you a lot of heartache when you eventually kill the bootloader, the display driver or both (and you will, it is part or the learning process).
In addition to the basic hardware care (checking for dust, reapplying thermal compound if necessary) you can run powertop to check what is keeping your CPU awake when it shouldn’t and take steps to purge unneeded services or resource-heavy applications.
It depends, if your docker installation uses /var, it will surelly help to keep it separated.
For my home systems, I have: UEFI, /boot, /, home, swap.
For my work systems, we additionally have separate /opt, /var, /tmp and /usr.
/usr will only grow when you add more software to your system. /var and /tmp are where applications and services store temporary files, log files and caches, so they can vary wildly depending on what is running. /opt is for third-party stuff, so it depends if you use it or not.
Their player works very well for my use cases: I use it on my Android phone, on my car via Android Auto, on my LG TV with WebOS and on my Linux machine via Firefox.
Yes, they have a 16bit/44.1KHz FLAC tier (€7.49), as well as a 320Kbps tier for lower data consumption and a 24bit/192KHz tier (€13.99) if you have the Hi-Fi gear to use it.