> Related to your links to best-selling computers, I've been thinking about downgrading to a low-spec PC as my daily driver,

my rule of thumb for the software I develop is - on my desktop computer (2016 intel 6900k, still plenty powerful) - there mustn't be any slowness / lag in any user interaction when built at -O0 with -fsanitize=address. This has ensured so far that said software had correct performance on optimized builds on a Raspberry Pi 3 in ARMv7 mode.