Pitbull Pleco's would be much more suitable, Otocinclus is suited to a larger tank due to its diet, which must consist of a limitless supply of algae, other wise they will just waste away and die.
Sorry but that is just not fully true. IF you don't have enough Algae feed them fresh veggies. Mine took to zukeanie fast. I have 2 in a 10 Gal tank yes they like to be in groups. I find keeping 2 in a 10 gal works just fine. They are in a small tank so they always see each other. I now have plenty of Algae and snail eggs for them to eat. They always have full bellies. I had one that would eat Algae wafers but not all will eat prepared foods. Most will take Zukeanie.
They are delicate because they get easily stressed. Being moved around too much and rough handling can kill them. It's best to pick your oto up after they have been at the LFS for a week or so. if you wait the weak ones will die off sadly and the strong ones will be ready for the new home. I love my otos and they are honestly one of my Favourite fish.
The pit bull pleco is a fish I have always wanted they to like to be kept in groups. So I say go for it if you can. I have only seen a Pitbull pleco once in my life but I read a lot about them. Basically they are larger hardy otos.
All amazon sucker mouth cats like to rasp on wood. It is not needed for the pit bulls or Otos. I have a branch in and my otos do love it but I don't think they are really getting the wood fibbers maybe.