There's more to the trim issue than just the different method of getting it done (trim tab on later 182 vs trimmable stabilizer on early 182 and all 180/185. The first few years after the 182 went to the wider fuselage and the trim tab on the elevator, the airplane didn't have much elevator authority. Talk to a lot of folks who have flown those mid year 182s and you'll find a lot of damaged nose gears, bent firewalls, etc. Cessna fixed that issue with bigger surfaces or more deflection (not sure which) in the later models.
I agree with Ryppa on the electric flaps vs manual. I have a lot of time in seaplanes with manual flaps, and a couple thousand hours in Cessna 206 on floats. Learn to fly the thing, and after a while you won't care which style flap it has. As to "popping" flaps, it has been my experience that, in general, this technique (and yes, I've used it many hundreds of times myself) does more harm than good for a pilot who isn't flying that plane on an almost daily basis. I've played around with popping flaps, rolling up on one float, etc, etc and it is my OPINION that if you're really in tune with the airplane, you don't really gain MUCH if any using this technique, WITH MOST FLOAT/AIRPLANE combinations.
That said, there are airplane/float combinations that are somewhat more water loving than others, and popping flaps can help a bit with those.
Finally, with regard to 182 vs 180, bear in mind that Cessna did a really lousy job of internal corrosion proofing on non-float kit equipped airplanes, and none of the 182s had float kits, early or late. On the other hand, many of the 180s out there have float kits, and all those airpalnes have MUCH better internal corrosion proofing. If you're going to go on straight floats especially, good corrosion proofing is essential in my opinion.
The 182s have not had float conversions long enough to see much in the way of bad corrosion issues, but I wonder if this is not down the road for those airplanes.
Myself, I'd want a well corrosion proofed airplane if it was going on floats.