If you use a dedicated smart phone (factory reset and everything) or a dedicated laptop pc (fresh install, not used for anything else) you should be fairly safe, that's true. I'd still go for a hardware wallet however. They don't cost that much and keep your coins safe even if physically accessed.
Disagree I don't think mobile wallets are that safe even if you take those precautions. The only wallets I feel safe with are hardware wallets or paper wallets because those are never online but rather offline completely.
To use bitcoin then an internet connection is a must, don't you know that basic? Bitcoin is a digital currency in the first place.
You don't need your wallet to be online to store Bitcoins, only to sign transactions. Using hardware wallets or paper wallets enables you to store your Bitcoins without having the respective private keys exposed to the internet.
In the end you still need internet connection to use your bitcoin.
Yes, but the private keys that give you control over your coins are kept offline, which is one of the main aspects of wallet security
Using a dedicated smart phone laptop PC you decrease the chance of getting infected by malware, but since the same device that signs the transaction (ie. being online) also holds the private keys to your wallet, your coins are still exposed to the internet, albeit briefly. That's not the case with hardware wallets, which keep your private keys offline,
all the time, even when sending a transaction.
Read here, for example:
https://doc.satoshilabs.com/trezor-faq/overview.html