Well, BTC isn't some asset that doesn't have a track record of growth. Take a look at the rate of growth in last decade. Yes if you look in specific timeframes it will look like a wreck. but looking at a bigger picture it makes sense. And it is given that it will keep growing similarly in the long term (Why?, thats a separate lengthy conversation the answer to which also answers why some of largest finance players are rushing to put out an ETF of BTC)

Coming to the security and safety part. In theory, BTC was made with a intension to be easily usable and accessible. Once you understand it, its pretty simple and straightforward (even easier than using a bank's service). No level of hardware wallet failure will compromise the funds because the funds are not in the wallet rather the record of the funds are in 100s of thousands of BTC nodes that is being run by miners and other enthusiasts. The real threat may be letting people that share OTPs to scammer handle their private key and seed phrase. Thats where custodians like coinbase comes in.

And to the point of how to make sure the fund held by ETF/Custodian is actually there or not, This can be easily verified. Tt is a public ledger and anyone with the public key can see how much funds are held in the wallet. This aspect of transparency is one of the key selling point of BTC.

I would recommend a short and interesting read - "Inventing Bitcoin".