One of the best ways of storing your bitcoin seed phrase is manually with a paper or any writing material. Your seed phrase should be far away from the internet, so making use of cloud storage systems is not recommended.
Not everyone is aware of how to set up an airgap device as the most commonly used storage is the mobile wallets. A lot of people uses mobile wallets and it's still reliable. The fact is that so long you are able to keep your keys safe, your are 80% free from having your funds stolen. Most crypto users have become too lazy to take the safety of their funds into their hands and thus leading to many losses that were unexpected. The worst that can happen is you having your funds swept.
Yeah, mobile wallets are also great i do make use of mobile wallet but, when your portfolio starts getting larger its recommended you climb to the next security level which is using a hardware. In using a mobile wallet, the most important thing is to keep your seed phrase safe and away from the internet, a lot of persons think they are smart by keeping their seed phrase in a cloud system, that's actually a dumb idea because because they just increase the risk level. It's best to learn from other people's experience than to let same thing happen to you before to start taking precautionary measures to keep your seed extremely safe to the best of your knowledge.