Don't trust wallet apps although you back up.
Desktop wallets and hardware wallets are the best if you just want to store it.
I wouldn't say that desktop wallets are best to use. Yes, it's better than web wallets and various apps. But there are risk involved - if you will get virus it's possible that it will steal your coins. It would be best to use desktop wallet on offline computer and connect it to internet only when you want to send BTC.
I would agree about hardware wallets, I'm using Nano S myself and I'm happy with.
You also forget to mention paper wallets. It's best and safest wallet for long time storage.
No matter which type of wallet you are using, it's crucial thing to save back up phrase or private keys and keep it in safe place.
Given that you'll back up so the risk was lower with desktop wallets but that's another thing with viruses that are also catching info remotely.
Well yeah, keep it somewhere that it can stored safely.