rockm

"From my understanding, I thought that only certain cultivars of European beech could produce that secondary budding, but that's why I'm still learning"

That may, or may not, be true. I don't believe it is. In any case, any cultivar of European beech is more responsive than American Beech as bonsai. I would, however, NEVER discount American Beech as a bonsai subject. It is a great tree to work with. It takes alot longer to work into bonsai, but hardly as slow as you seem to think. It is very vigorous once established in a container. It is also extremely winter hardy if it's native to your region. It can take shallow containers too.

It isn't a beginner's tree, as it requires some specialized care, but it's also not THAT difficult. You just have to double up the development time expectations for this species.