Check out Scuba fins. They really move you and if you lean back and flutter your feet like a swimmer, you move on the up and down stroke. I think they take less energy than FF and I have both.
There are several around here that put Minn Kotas on the V tubes. Not very hard to do but then you have to license them.
I think you are doing it right. Getting the Tubes now and later a pontoon.
I have several pontoons and found myself looking for a light weight tube for a few lakes I love.
Those Tubes would be perfect.
There are web sites out there that have some killer home made rod holders for them as well.
Sky is the limit: