No mentions of Apex yet, but that's what I've been using on my last 3 phones - S4, Note 4 and S8+.
Do you remember shell replacements for Windows 95 and 98 back in the late 90s? Explorer was the shell and 3 examples of replacements were Darkstep, Litestep and Talisman. It's not a huge thing for Windows any more, but that's what a launcher is - a shell replacement for phones. An Android update won't interfere with the launcher. At the same time, launcher's own updates won't interfere with Android. Very occasionally, the phone will ask you which launcher to use, select your preferred one and select the box to always remember that option. I think I've only been asked that once in 12 months.