I'm with you on growing more things vertically! I haven't grown most of the things you listed in eBuckets (yet), but I think you should stick to one plant per bucket for most of them, except for peppers and bush beans. I have one bucket with three sweet peppers this year as a trial, and so far it's doing well (see picture). I haven't done bush beans in a bucket yet, but based on my experience growing them in an Earthbox, I would say you could fit 4 bean plants per bucket. If you plant pole beans in an eBucket, I think you can go up to 6 or 8, using a Maypole-type trellis. I planted six, and they're doing well so far.