This is how i keep my private keys safe since i can't afford to buy a hardware wallet.
1. A complete new harddisk
I bought a new harddisk and install window 7 on it and copy all my private keys in there, i don't bother to leave this harddisk in the pc, after the copy is completed i remove the harddisk and keep it.
2.My Recording book
I have a long hard shelled book that i use for keeping records of all the airdrops and bounties i promoted because sometimes i used to forget easily so i write down my recovery seeds in this book as well
3. Flash Drive
I have a good 8gig flash drive as well that i use to copy software and files from one pc to another so i format this flash drive and copy my private keys and recovery seeds in it.
At first no one knew i am into crypto stuffs and secondly i don't share my room with anyone cos i am living alone, those who have people around them with face problems like friends going behind your back checking through your stuffs or even stealing your things, hardware wallet is still the best though.
having lots of backups and airdrop and bounty notes is very useful, but protection must also be extra. If you use a flash drive and a special hard drive, you need to provide more protection for the Private Key by pressing it and then give a password, it will be safer if there is malware that suddenly attacks your device. Make sure Antivirus remains updated.
I use wallets with local passwords like metamask, but this wallet will not require entering the Private key regularly. The remaining is to keep the Private key safe by printing it on paper and keeping it safe, and finally, Security for my computer.
Metamask is also very good, I use it for transactions in decentralized exchange to be more secure without the need to enter the Private Key again. But be careful about fake metamask too, be sure to download the original extension on the official website. or check again before downloading.
All of them that you mentioned on the above post is good way but, everybody has own strategy to do it. l prefer flash disk or mobile, pc wallet. In my view, it is better way instead of using web wallet. When you are using web wallet, someone can steal your coins. There are a lot of ways to do it, but we must be careful if the security vulnerabilities are not solved yet. If you hold your private case on your phone, it can be stolen, it would happen in one day, you can lose everything.