How would you store a very large amount of crypto currency
I am very happy with my Trezor, less so with my Ledger (because I find the interface annoyingly clunky).  The Trezor is extremely easy (and, I believe, extremely safe as long as you don't leave your PIN number or recovery phrase lying around).  It works fine for Litecoin and Bitcoin, and a bit more annoyingly for Ethereum (where it outsources the wallet to another provider).  I don't believe it will hold NEM.  I'm not sure if the Ledger will hold NEM, but it should be easy to look up on their website.  I hold only Ripple in my Ledger, because (among the coins I hold), this is the only one the Trezor won't handle.