Is there herbal nootropics that are both powerful and legal?

Bacopa is proved to enhance memory. In fact, it would be the best long-term memory enhancer I've tried. I suggest you give it a try, although it does take time to notice the effects; but hey, you don't lose anything by trying.

Why does it have to be herbal? There are plenty of other non pharmaceutical supplements that work very well and there are some very safe pharmaceutical ones too. For cognitive enhancement, there have been studies showing strong but different effects for American and panax ginseng. Axon labs makes some good stacks if you're willing to,go beyond herbal adaptogens

What are your goals with an herbal supplement?

Are you anxious, trouble focusing, do you have sleeping problems, want to prevent degenerative brain diseases, or increase cell apoptosis?

There are a lot of reasons to take herbal supplements. But in order for it to be effective, we need to know what your goals are or any issues standing in the way of your goals currently.

For example say your goal/problem is you have trouble focusing for extended periods of time. So you would need to increase choline, dopamine, add a long acting stimulant, reduce burn out... ect

So probably a combo of:
Alpha gpc, huperzine A, mucuna pruriens, bacopa, theobromine, caffeine, l theanine. And from there tweak the stack depending on how you feel.

But to have the most powerful impact, you need to know what can be improved upon in yourself.