Pretty much.
It is cheaper new, but more expensive used compared to an FE plus those parts, so it end up being roughly the same overall, the only differences being that the F2 is supposedly capable of higher joules, and it has a clicks microswitch trigger while the F2 has a switch with zero effort at all.
The F2 does have the advantage of auto aligning with your old gearbox, while the FE sometimes requires shimming to center the nozzle to your bucking entrance, but that doesn't occur nearly as much as you may think.
The F2 in theory is les efficient than the FE after those parts and tuning but is more efficient out of the box, and the Kythera seems to be a bit of an odd duck like you said as it's supposedly the most efficient due to all air being used to fire the BB instead of venting a valve for a millisecond, but nobody I've talked to seems to be liking their Kythera, and some have sold them and gotten other engines.
About the shot counts for any engine, I think it's reasonable to be really vague like Polarstar, Redline, Wolverine, Raven, and the other ones are as everyone has a different bucking, barrel length, barrel bore, BB size, BB weight, and literally everything imaginable different, they really cant give a precise number, so they lowball of be on the safe side.
I am currently trying to sell my HPA body so I can buy a cooler one that weighs less, plus a different inner barrel and maybe hop chamber, so I can't give you consistency as I forgot what it was.
I do recall it being bad as I was figuring out R-hop, different nubs, FCU settings, engine stability, different buckings, and everything else, but I do think there is potential to be good as I have a friend who gets +-2 FPS with an Elite Force .32g BB at like 1.7J.
When you start getting parts for your gun, I suggest the following from my own experience.
MAXX ME Sport(you only need the standard arm that takes regular nubs)
G&G Blue flat hopped
FOW nub from shapeways or H-nub style nub
Action Army 6.01X??? AEG barrel(I used a Lambda 6.01 and liked my AA more)
R-hop for Action Army barrel
Plastic gearbox or RetroArms gearbox(purely weight)
For mods I would suggest
Barrel spacers made out of clear packing tape
RTV glue your bucking to your barrel over your R-hop for 100% stability and seal
Shim your hop chamber to keep to centered
Line every hollow cavity with aluminum tape and some sort of foam, even that 2mm craft foam sheet.
Besides all that, I strongly recommend First Strike tanks with an SLP spring(200-400 PSI) and I would suggest .40g-.48g BBs as that's what gave me the best results in terms of vertical and horizontal consistency as well as effective range and efficiency(since you get more joules with a heavy BB you can lower you PSI and adjust your FCU so you end up using less air to get the same joules as a light BB.
If you do plan on using light BBs I'd suggest steer clear of R-hop and similar systems as they don't usually play well with HPA since they won't hold the BB in place consistently due to less required pressure to apply adequate backspin.