Coz I'm sat doing nothing I will add to the pot, match kits are typically three sections and power kits are two sections. A lot of people remove the top section from a match kit leaving it as two sections and use it as a power kit.
Puller bungs go into the end of a top kit in the same way as a normal bung but a tube carries the elastic to the end of the kit so you can pull the elastic thus increasing the pressure on the fish. Although there are a few different manufacturers of puller bungs, once you've seen one you've seen them all.
Side pullers exit via the side of the top kit (as the name suggests). There are several different designs of side pullers ranging from a simple PTFE bush through to a slot and a bung with a wheel. Side pullers require the top kit to be reinforced where the exit point is.
There are MAP side pullers, Preston roller pullas, Maver easy flow bungs, Drennan Roller cones (only available with drennan to kits), Vespe strippers, Frenzee easy glide and probably several more.
The advantage of a side puller over a puller bung is you can reach up and use it even if you have not fully broken down to the top kit (e.g. fishing water deeper than the top kit so you are fishing a top kit plus one). The advantage of the puller bung is that the top kit does not need a reinforcing wrap or drilling.
If you go the puller bung or side puller route and your topkits are rated to say 20 elastic, you will get away with using a lighter elastic due to the fact when you pull on it you are putting more pressure on it, I have side pullers in some of my kits using from solid 10 elastic to 17h hollo elastic, and funny enough I rarely use them preferring to play the fish as normal. I have seen anglers fishing open water and stripping elastic like it was going out of fashion just because they have pullers fitted. I will use mine if fish are heading for a snag but on the venues I fish that is rare, I have removed the number one section from my match kits and have single strand of number 6 elastic on a standard winder bung on one kit and double number 6 on the same set up on another, A tip if using side pullers is to use a longer piece of elastic than required and slide a snug fitting rubber bead onto it before tying off where it exits side of pole section, This acts as a tensioner, have the bead down to the section for a tighter set up and away from it to fish with softer set up, you can still strip elastic if required when playing a fish.I usually have mine down to the section when fishing across to an island, it is set tight enough to slow a fish down on first run,