I've been casting flies from a kayak for a few years. I have a touring kayak, nothing fancy, but it will get me pretty much anywhere I want to go.

Compared to a float tube, kayaks have advantages and disadvantages:

Kayaks will blow around in the wind unless you anchor them.
You can't paddle and cast at the same time from a kayak.
They are heavier to carry around than a float tube.

On the other hand,
you don't need waders,
You can cover a lot more water,
and you can exploit that blowing around by paddling upwind and allowing the breeze to carry you back, trolling a woolly bugger behind you.