same setup here more or less. changelly through ledger live most of the time, changenow if the rate's better on whatever pair i need. i used to compare every time but on normal swap sizes the gap is usually too small to care about, so i mostly gave up
the wait time thing catches everyone. first time i swapped BTC to something i sat there refreshing convinced something had gone wrong 😭 turned out it was just waiting on bitcoin confirmations. ~10 min a block and you need more than one
If decentralisation isn't a priority for you, Changelly and ChangeNOW are perfectly fine options, and they're integrated into various self-custody wallets. Personally, though, I'd prefer a DEX like Uniswap for serious dealings because, despite Changelly and ChangeNOW offering swaps without requiring a conventional custodial exchange account, they're still centralised intermediaries in the transaction.
But that's by the way, as I suppose your fees and speed experience are the major reasons for your post.