Love watching my juvie BN plecos do this to my mystery snails. Such a cute sight. With this much better picture of the plecos you have, it is pretty easy to tell you what they are. They are juvie bristlenose (BN) plecos. These guys will eventually need a 20 gallon tank (for one) once they grow.
Once again one lucky Betta. Plakats are my favourites as overall they are a lot stronger fish, you made the right choice. I find the veil tails struggle with their finage especially when they get older. I so wish we could stop the cup trade of Bettas. It is barbaric, luckily I have never seen this in the UK, there would be an outcry if there were. The LFS can benefit from showing these fish in aquariums as they can then up sell the overall set up. You are a credit to the Betta world.
In respect to your plecs, see if you can get hold of some Oto's, as these remain small. You need a group of them, a mature aquarium, and wait until they have been in the LFS for about a month, as there is usually a high mortality rate post shipping.
I want to start adding plants to my Betta tank. New to them. I think I see water wisteria and Java fern. What else works good with a basic setup with a small led light bar? The Tetra one. It's on a 5.5 gallon.