Thanks for all infos @OmegaStarScream, really useful!
I believe that paper wallets are the most secure way to store bitcoins if you have big amounts and want to hold it for a good time also you can make 1 wallet for every bitcoin for example and have more security.
Paper wallets are easier to get damaged, and won't show if tampered with. The best way is probably with DIY physical bitcoins, with a QR code. Those have holograms which show if tampered with, and stand better against water.
Just put a plastic over it, make three copies, hold one with you, let the other in your parents home and the third one put on a bank safe box...
Physical coins are fine too, also you can grave in some metal too, there's a lot of options.