What a nice aquarium this is going to become as the plants establish and grow, and with the fish. Water parameters are perfect too.
I would increase the rummys, they are always better with more; fifteen would be my aim.
Marble hatchetfish would be good, no less than 15 here too. Just keep the tank well covered, you know why.
The Emperor I would not include, not with this combination of fish. I have a group of Emperors in my more active tank, and they are better suited there than in a tank with what are sedate fish; I had to move mine for this very reason. The rummys are the most active swimmers here, but even they are relatively calm by comparison to Emperors.
Whiptail catfish are very nice, they are extremely peaceful, and add some "unusual" interest, always making me think prehistoric. The common smaller species in our profile, Rineloricaria parva, is the one you want. Or for something different, the red variant, in our profiles as Red Lizard Whiptail. I have a trio of these in with one R. parva, they go their own way.
The pleco, now described as Peckoltia compta
is a fish I have not had, but from what I can find out it should be OK with plants. It is primarily carnivorous, not touching algae much if at all. Gets 4-5 inches. Best on its own, as it is territorial. Peaceful with other fish. However, one big drawback here: it needs a decent water current, as it occurs in moderate to fast-flowing streams over rocky substrates. All the other fish are quiet water, so this is not a good match. And, such fish can be a problem with sand, rearranging it and uprooting plants in the process.
Hope this is of some help.