1) Nope, not going to recommend any.
2) This depends on what temp range you are out in, There are tricks to using "toppers" down to about 20-25F. Remote canisters can be used down to as cold as WG stoves...usually with no real weight savings, though. Fiddle factors become important. Fuel efficiency, cost per Liter, maintainence, reliability, etc all become part of your decision. Generally a topper starts failing at about 40F. Freezing is "close" to the limit using no tricks.
A remote canister stove is better, at least with temp range and usually with fuel efficiency. But, these are invariably heavier than "toppers" because of the additional supports and hose needed. This means more fiddling with connections and set-ups before you can start them. Some are real good in cold conditions. But all of the good ones in cold conditions require a bit of "priming", in the sense that the preheat loop needs heating. Roger's stove uses a metal heat conductor witch will take longer than a loop. But, still the time is short. (His stove is also about 3.25oz, about the best I have heard of for this class of stove...better than a lot of plain "toppers".)
3) Pot diameter is a trade off with surface area to absorb heat and surface area to radiate heat. Taller pots radiate more than shorter pots. They also absorb more. Heat Exchangers are nothing more than increasing the surface area of the bottom to absorb heat better. An 8" diameter pot nearly bottoms out a camp stove on low...increasing diameter to 9" does nearly nothing. Anyway, thare are too many variables to say one is better than another. But generally a 5.5-6" pot about 2L works for all conditions for a group of 3-4. On very low heat, a smaller 5" pot works nearly as well for smaller 2 person groups. Heat screens, like the Caldera set-ups, also use the sides to absorb heat.. These are excelent solo, sometimes 2-person set-ups.
4-5-6) ignored for now.