1. Where do you post (or find) cash trade offers ? Localbitcoins, Paxful, Bisq, Localcryptos, Bitcointalk, Craiglist, or...?
I don't get you well here, do you want to know other examples of p2p market places?
2. What is one thing you would like to change from the platform that you use now to make your experience better ?
It's quite hard to just brainstorm minus knowing what features the platform will have.
Maybe you can first outline what your platform will provide then we add on what we think could be nice but missing from the features.