Ask HN: Protecting Family Computers

I live a conservative online life - I have separate emails for friends, for business, and for crap; I don't open strange emails or download attachments; and I have spare computers if I really want to touch a potentially wonky website. I use Keepass and try to pay attention what I'm doing. So on my Windows computer, Windows defender has been sufficient. I can't claim I'm 100% certain my computer is not compromised (can anybody these days?) but have not had any issues.

My family... is different :-). I'm constantly cleaning up weird browser extensions, strange software, cancelling subscription, etc; and their email inbox makes me cry.

Should be paying and installing something like Norton or Kaspersky or McAffee? Is there a point? Do they create privacy / nagware / ads / performance issues of their own?

How do you set them up for backup? Backblaze or sync.com? Or is there a simple utility I could set up to e.g. backup daily to SD card or something?

I assume I'm not the only person on HN to support family, but my work has taken me away from personal laptops (I spend my time either on AIX command line or in Powerpoint:) so I'm just not up to speed with that stuff anymore - any help appreciated :)