It is hard to say from the pic of the pleco-if it is a common pleco it will get about 2ft long and will need a much bigger tank, I would look it up and see if you can ID him
Do you know how many gallons the tank is-measure it and I can tell you-it looks like a 10gal but it is hard to say and if so, it is too small for any species of pleco.
Your tanks looks nice by the way...look forward to seeing it once you have it all set up and planted and pic of your new Bettas...
It looks like a King Leopard pleco to me. Beautiful fish and amazing sail-fin when he flares. However, this is one of the breeds that gets pretty large- 1.5-2 feet. I got one at 2" and kept him to 5", which took about 9 months. I took him back to the LPS and they were happy to take him and resell him.
I did find that this breed has larger teeth than most plecos do, so instead of scraping algae off of plant leaves, they tend to chew THROUGH the plant leaves. I thought there was something wrong in my tank- never stopped to guess that little bastard was the one eating all my plants. He couldn't chew through the anubias nana, but he ate any sword or otherwise thin leafed plant I put in the tank.
Definitely no on the pleco, however, a ten gallon is perfect for a single betta with a school of pygmy corydoras catfish or for a few females. 4 is a good number for a 10 gallon tank, but I really don't recommend sororities for beginners--they can be tricky, and you have to acknowledge that not all females will cope with a social situation, some just cannot live that way. If you happen to purchase one of these females, you have to be prepared to house her in a separate container permanently. Also, keep in mind that a sorority can be fine for weeks and suddenly erupt into chaos--you may have to make important decisions about when to separate them and how to treat them when/if they become injured. If you do decide to go this route, you should do a lot of research before you start.