I believe binance as the exchange isn't the best to store coins, in my case.
not just in your case, it is not a good idea to store anything with third parties when these third parties are scamming users left and right.
but sometimes depending on your trading strategies, you may need to have the altcoins ready so you can dump them as fast as humanly possible so you hold them there but only for a short time.
But what about the rest of the online wallets, they can be hacked too and the physical device can be lost.
but anyways just trying to understand if my simple USB flash drive with keys inside the encrypted folder would be similar/same as ledger device..
only cold storage is safe. and that is when you create your keys offline and store them there.
usually people go the easy rout and buy a hardware wallet and hold some altcoins they support in these devices.
if you store anything on your USB disk then make sure to have additional backups as much as possible like printing your private keys on paper so that in case your USB disk died you still have some safety net.