I am a 7D user. AF on rear AF-button, AI-Servo-Mode, single AF-point, matrix metering, EC +2/3 EV, slow series drive speed are among my default settings in all modes.
the 3 presets are used as (starting point) for the following "special modes":
* C1 - "snapshot mode" ... that I switch to, when a person not familiar with my camera wants to take a shot ... = P-mode, Auto-ISO, low-series speed, one-shot AF, automatic AF point selection, jpg, AF on shutter button, custom functions mostly set to default
* C2 - "tripod mode" - Av f/4, single shot, one-shot AF, single AF point active, ISO100, LiveView active, mirror-lockup, self-timer/IR remote control with 2s delay, plus some more settings - eg. noise reduction on long-time exposures
* C3 - "action mode" - Tv 1/1000s, fast series, AI-Servo-mode, AF-point extension, ISO 400, and a few more settings e.g. flash sync on second curtain, etc.
in C2 and C3 I adjust parameters if/as required in situation, but do not overwrite register with changed values. That way I know exactly, what I get, when I turn the mode wheel to C1, C2, C3.
Advantages of AF on rear button - please use search, this has been discussed many times over, no point for me to repeat.