A few weeks ago I installed an M.2 SSD drive in my primary workstation, and just today I installed a second one. The complete story is a bit long for a post and it really belongs on my technical website, the DataBook for Linux.
The article, Converting to SSD, covers the initial conversion and then the addition of a second M.2 SSD and the problems I had when migrating a swap volume to the SSD. It’s probably not what you think.
Anyway, I hope it helps.