question about RUBBER LIP PLECOS?

Rubberlip plecostomus reach about 6" in length as adults.

Depending on your current stock, a 33 gallon would be considered an adequate sized aquarium for a rubberlip.

They probably won't bother live plants.

They're fine on their own.

You'll want to supply them with some soft real drift or bogwood, as most plecostomus require wood to rasp on. They should not be relied on for algae control, and should be fed algae wafers and blanched vegetables. Skin-on zucchini slices are good for them as well.

No, they aren't terrific algae eaters, but algae eaters are, and you could keep two of those in your tank too to control it. Also, my not be a priority to you, but aquariums generally look nicest when you can see the fish, and since plecos or algae eaters aren't super active or pretty necessarily, so to make it look nice you could get a school of tetra or something like that. Just personal opinion, but it would really make the tank look nice, and would require very little extra work to care for.