That's a very healthy and well grown vanda. I think you've done an excellent job of growing it. Congratulations.
I live in South Florida where there are lots of commercial vanda growers. The roots on the hundreds of vandas in their greehouses look just like yours. I don't know if it's algea of something else but I see it on vanda roots all the time. I suspect that it's not algea because commercial growers use fungicides on their plants. I don't think you need to worry about it at all.
Personally I wouldn't try to remove the basal keikies on your plants. Every time I've removed them I've always been sorry I did. my opinion is that vandas with multiple keikies make spectacular specimen plants when the keikies get big enough to bloom. If you really want to break up the plant for some reason, the keikies almost always survive very well but it will take years to grow the plant back into a big specimen. Good luck.