To use multiple wallet may one type of solution, but not longer, as what I believed. Right now, I'm using Electrum mobile wallet that gives me pleasure!

We can easily lose them don't you think?
But we can have them stored in PC, not the one you use some other PC? or you can use USB drive.
You can protect your PC by using some antivirus software with high security features.

I'd never use a paper wallet actually...It seems like the least secure way ever 

If you don't have a lot of bitcoins, i think it is quite safe to keep them in online wallet. Of course if you have more, you should keep them in cold storage. It is not that hard to make one, and it's probably safest way to keep your bitcoins, as long as you don't lose/destroy it.

I really wouldn't recommend you to keep bitcoins in exchange, you probably haven't think of it, but if you did then don't. It's very risky to keep your bitcoins there.

If it is an investment to HODL you should have cold storage.
If you need to spend them and use them for trading - then you need hardware wallet (like Trezor or Ledger)
That's it

You have a small amount, and you will do trading means use any online wallet it is easy to way to transact your bitcoins with one site to another site. Or you want to save your Bitcoin for a long time use offline wallet. Electrum is the best wallet to save your bitcoins. Before I used to save my bitcoins in blockchain but now I shifted my bitcoins to Electrum wallet.

Don't know why people don't trust e-wallets. I have several years of using online wallets and there was not a single case of hacking. Always quickly and conveniently transfer or receive bitcoins. I think offline wallet is uncomfortable and it does not guarantee 100% safety.

Kepping only cold storage wallet is not convenient. You should have two wallets, one for everyday transactions, and one "cold storage" for your savings.

Well, therefore every hard wallet both online and offline has a secret key, we have to backup the secret key data, in some places that allows us to save safely, and recommended not only save one data.

To all those who swear by paper/hardware wallet, how do you then store and secure it?
It seems to me you are solving the risk of hacking but introducing the risk of losing it/being stolen in an old fashioned way.