I am not much bought into idea of pure FOSS .. I think Debian is kinda annoying as first thing people do is allow non-free :-)
never tried Arch ..cuz ..as you said "if you want LIFE " :-) which I do .. but maybe one day !
On customizability .. I was (once upon a time) deep into that rabbithole :-) .. wasted lot of time with NixOS .. good learnings but at the end if the day , I realized I only use fbterm, ssh , vim, tmux and w3m .. so plain Debian on a 32 bit machine ..hard wired with internet .. big mug of coffee .. ton of tobacco .. LIFE :-)