Depends on what light you have. If your lights are weak, then stick to low light plants such as java fern or anubias.
Strong filtration only help pick up waste, which makes weekly water changes (siphoning) easier. 5 is way too much. After all your substrate and rocks, you seem to have less than 15g of water. Otos only add to your bioload and give DPs tankmate.
I want you to have long term success. Best thing to do is get 2-3 DPs. 5 would pretty much make maintenance very difficult since you would have to do more water changes. The less maintenance you have, then the harder it is to keep these fish. The failure rate of keeping these fish is high because too many People try to put too many DPs in a small body of water.
Males have wrinkles behind eyes and i think its their most distinguishable way to sex. Look closely.