Hi,
Which are the best cold wallets for these alts?
The best cold wallet is generally stored in your freezer.
Just kidding.
There isn't actually a direct cold wallet (hardware type), however you could download the actual windows/lin/mac wallets and then save your wallet.dat file if you're technical and know how to use it; transfer it to a usb drive and save it that way.
Most people currently keep their esp staking though.