You don't understood enough. BTCB is a 'bitcoin-backed' solution by binance... in the same way that it is WrappedBTC (WBTC) for example.
You can keep your BTCB on your ledger (as I'm doing).
What is your 'wallet'? Lol, what a shitty one. Get yourself a ledger damn. I can't understand why people 'wait' that much before purchasing something that should be #1 priority.
regarding AVA, buy the minimum that you need to stake and lock it into Smart (and forget). This or hold on Ledger. No need for exchanges.
Take care.
RE: (Bitcoin Challenge Update) - Moving away from Celsius, say hello to Venus.