Our platys are about 1.5" and only had them about 4 weeks and they are messy
but ever so pretty, maybe it would just be a case of deciding what you can commit to long term.
For me the maintenance is a part of fish keeping and helps me to keep up with my tank so the platy mess is just fun
As for corys we havent actually kept them as yet so I really would not like to comment! Im a newby and as such postage stamp knowlege lol
Maybe you could just get prepared as your LFS was closed as it appears your approach is to investigate then move forward and in the long term this will give your far more satisfaction as a fish keeper!
We have bought, in excitment and this has led to regret so all i can add is good luck and keep remembering slowly slowly gets the best set up, moving fast means errors and these can be costly!!
Take care and enjoy your tank, I am still
ing over you getting a tank to yourself.