They have their own DEX, why dont you download your client and start storing your coins in there? if your pc is safe, there is nothing of what you should be worried about.
But I became sceptical, since I found no way to store my coins, in a wallet, that's convincing secure.
You are trying to look for a wallet that accepts Waves, but none of them (trezor - ledger) are accepting waves, because it is a coin that doesnt have much marketcap, and it is not having a huge demand at the moment.
Using an online-wallet does not give me the impression, that my coins are secure: what if the online-plattform gets hacked or corrupted?
Use their dex, that is one of the most safest things that you can do