Not sure if this the right forum for my topic, so happy for a mod to move it if necessary.

I've recently decided that I (and my household) need to better with my digital/online security, and one of those areas is (potentially) a VPN.  I've been giving it some thought over the weekend, but wanted to check a few things here first.

I guess the key question is what do I need a VPN for?  Most of my (and my wife's) online activity takes place at home over wifi or ethernet, on our smartphones over a mobile data connection when we're away from home, or at work-based wifi.  My wife sometimes uses public wifi at the library.  I rarely use public wifi, but there are occasions (like last week) when I do use public wifi which is what prompted me to think about VPNs.

The way I see it, there are a few use-case scenarios:

1. Browsing over a public wifi connection away from home on a mobile device.

2. Browsing over the cellphone data network.

3. Browsing at work on my employer's wifi network.

4. Browsing at home on my home network.

Is it reasonable to infer that my browsing on my home network is generally "secure" (insofar as any home network is secure), as browsing on my mobile data network, but that the other two scenarios may be less secure?  To me, this would suggest that I don't need a VPN at home, or if I'm just using my mobile data connection on my phone.  I'm not especially paranoid about snooping by the ISP, so I don't really think I need a VPN in those situations.  I should also add that I'm really thinking of a VPN for a unblocking geoblocked content.  I already use a geounblocker which I'm happy with, but I'm aware that a VPN can also help with geounblocking, so that's why I'm including the browsing at home aspect in my considerations.

For the work wifi, I'm not particularly paranoid there, but I was considering whether an employer that provided wifi would prohibit a VPN, as it hides what content is being accessed.  Is this likely or common?  I know I can ask my employer, but I'm curious whether this is generally accepted that a VPN can't be used on the work wifi.

For the public wifi, a VPN seems a no-brainer.  Thinking through the whole thing, it seems to make sense that I should have a VPN for accessing public wifi, but possibly don't need it (or won't be able to use it) for the other scenarios.

Then there's another aspect which I was wondering about.  For most of my thinking I've been envisaging a VPN managing data flowing to and from my device to an external endpoint, but I'm aware some people use a VPN to route access to their home network.  I don't really understand how this works though.  I get the impression that you need to run software on your router, and that what you're doing is connecting via a VPN to your home network, and then everything runs from there.  Is that a better overall solution?

It's all a bit messy, because I'm not really sure what I need, and how it would work.  There's also the question of which VPN providers are worth spending money on, or whether I need new or additional hardware.  Is there a reliable guide to VPNs I can read?  I've googled a little, but I mostly seem to be getting myself more confused.