I appreciate what you say. Over past 14 years, I have had many backups, but couldn't recover any of them successfully. This points at the value of your statement "The ability to restore if needed is the whole reason to do backup. Make sure you can restore, in case of a whole range of potential problems".
I forgot to mention that I have an UPS (make: APC) installed in between the main power supply and the desktop PC. The software it comes with winds up the entire work, saves all open works, and then shuts down the system, with its 45 minutes power backup. Though, never a situation has arisen for APC to put it software in action over the years, yet it can only address one of the issues you have enumerated in your reply.
May be, I have been lucky so far but that does not guarantee my safety for all times to come. And, therefore, I realized the importance of your statement "Store this drive somewhere else". In other words, I mustn't use a drive that is an integral part of PC, connected through SATA and Power plug. What you are suggesting sounds like 'use an external case in which I can place the backup drive, and disconnect it from the PC after the job is done; and then, move the drive away and keep it somewhere far enough'.
Thinking on similar lines, 'can a portable drive like Seagate Backup Plus substitute the 'external case containing backup drive' so long the portable drive is disconnected after every backup, and removed from the vicinity of the PC it was attached to while taking the backup'?
One question comes to my mind: should I be taking a full back every time, not an incremental or differential one?
Now, on the question of cloud storage. If a corrupted file gets uploaded from my PC to my OneDrive account, or Google Drive account, do they not monitor the contents for any kind of threat using some very powerful software, on an ongoing basis? If not, then it's hardly worth paying them monthly fees for additional storage space on recurring basis?
I couldn't understand what you meant by "you better round up a pile of Bitcoins to get your data back"?
Best Regards...