Welcome to the wonderful world of waterplanes :-)
I'm no expert, and have ZERO real world experience of floatplane operations (that's my disclaimer out of the way lol), but so far as I understand it, float pilots generally make a low pass beside their intended landing channel to inspect it for debris like logs or other obstructions, before circling round and landing.
Checking the wind in FSX ... I don't think it's possible to have the water textures lined up with the wind, so I 'cheat' by using Shift-z to look at the wind. Smoke from cabins, as you note, can also help, although it can be really hard to see.
Its a good question about cross-winds on rivers or narrow channels. My thinking is that dipping the upwind float isn't going to work as landing on water is like landing with the brakes already on. The massive drag on one side of the aircraft is going to lead you into a whole heap of problems.
Just my amateur tuppenceworth.