Dear Csound1, please accept that I am not trying to be awkward; nor am I totally ignorant of computers, nor of other technical matters, having a degree in physics, having taught maths and having worked as a development engineer in musical electronics before becoming a professional and academic musician.
Leaving aside the nomenclature, I understand that I essentially have two options. I can either store all my data externally in such a way that it does not update when I change files on my computer; that is what I believe you mean by 'backup'. Or I can store it so that it updates every time I change something on my computer; that is what, rightly or wrongly, I have been calling 'backup' and you have referred to as synchronicity, and it is what I want, even though I realize that it is no insurance against an accidental deletion.
If I change my mind after I have uploaded all my stuff to Google Drive, I can set the Google Drive app. so as not to sync any further. I shall then have the first option.
The same two options would be available to me if I used an external hard drive instead of Google Drive. In fact I am thinking of obtaining an external hard drive in due course. In that case I can have both options simultaneously, one on Google Drive, the other on the external hard drive.