H264 vs H265 .. iirc also depends on the software you may use for alerts / triggers / AI - ML .. so want to check if there is a difference between those and what software you plan to use.
FPS .. many run at 15fps or even 8 fps to reduce load on system .. and storage space ..
Blue Iris .. also many like to set iFrame = fps ..
also try to maximize the capacity of your HDDs ..