Rdwc

I think it will be enough movement to oxygenate your solution. If not you can always just provide it at the primary rez. Now how practical it will be will depend on your setup, you might be ahead to just do a NFT system. It would probably be a lot simpler. FYI sidenote- When doing airstones, larger bubbles may provide more agitation but are actually less efficient in providing oxygen to your solution. Many smaller bubbles have more surface area than a single large bubble of equal volume. So the smaller bubbles provide more surface transfer of gases.

The agitation on the surface film won't be enough why don't you try bigger bubbles and take the airstones off the end. Same result...

RDWC is good in theory. In practice they can be very different. Consistent tweaking because your setup isn’t just right. If running multiple buckets one plant always outgrowing another because of an inconsistent flow of nutrients. If you think you’ll get by without introducing air, good luck.

It will be more effective. bubbles suck and only good for a small bucket of water. Any type of churning of surface is 10x more effective than air stones. As long as it can mix the top/bottom volumes it's good. Waterfall may only be effective at that to a certain depth. A waterfall per bucket is fine too, but bad design... a lot more equipment and wasted effort than can be done much more simply. A powerhead or 'wavemaker' is a better option and kills 2 birds with 1 stone by also mixing the water for you too. Drip from rdwc is essentially oxygenated as it occurs, too. Gas goes into solution almost immediately. Increased surface area (over time due to churning or a drip) will quickly pick up O2, if not already saturated. With rdwc, i assume you have a large reservoir and the water flows back to it? That's a lot of excess maintenance, if not. So, a powerhead in your rez will be plenty. I bet the drip at the plants would oxygenate itself enough but it's only 10-15 watts to toss a powerhead in rez.

if it works for fish tanks I think it would work for plants. My only concern would be if the roots become a large mass if the DO will penetrate. Should be ok though. Maybe wait till a more experienced hydro person chime in.