Lancelot,
I'll give you my perspective, FWIW.
I would say it come down to a couple of questions. If you have not tried any other type of grip that is deeper towards the back, you might want to get the extras. Probably cheaper to try the kit than to try buying other makers extended grips. If your fingers are a bit long, or in my case, you do precision shooting, you might like the extended backstrap. Your avatar indicates that you might shoot with gloves. I like the deepened trigger guard for this.
As to the various compartment accessories, I thought that I really did not need to worry about that. Turns out that the insert for the 3 spare cartridges can have the rubber cartridge insert removed, and you can just use it as a cap. Lots of room for goodies, like my 1/2 wrench that is shorted to work with my Nightforce ring nuts. There is a lot of flexibility with the entire kit. I am not really changing components for different situations. I just found one combination that works well. Lightyears ahead of the standard configuration.
Craig