I remember saw comparison before, although lower resolution 500s actually seems a bit clearer, the only bad thing is the weird aspect ratio that some people may think it's so bad

70mai also releasing new 4k (a810?) soon

digital optic is not so straightforward, there are many factors (lens, sensor, compression, codec, etc)
higher resolution is not always equal to higher quality image
and most of the time those normal consumer grade product they won't list very detail tech spec also, so quite impossible to know if just reading from spec sheet
that's why for commoners it's easier just check other people review or see it yourself

diy pasang, just search in youtube your car model and install dash cam, almost every car can find
if you connect to cigarette lighter socket easiest no need mess with fuse box
more troublesome usually is hiding wiring to rear but if you don't care too much you can actually just let it expose like that