I’ve installed gpg4win and created certificates, but I’m not finding a connection between Kleopatra and the windows 10 mail client. Do I need to use thunderbird in order to get Kleopatra to integrate with my email accounts, or is there a way to get it to play nice with the mail client for windows 10.
Additionally, I’m not sure if I’m going through a lot of trouble for no reason - i.e., do I need to bother with gpg4win if I’m using Tor, ProtonMail, and Tails?
To your general question:
Gpg4win gives you end-to-end crypto capabilities that can be independently inspected
and that use standard communication protocols. The crypto capabilities include
protection of integrity via signatures and confidentiality. The OpenPGP and CMS standards
allow communication via offline channels and several trust-models to manage the necessary crypto-keys.
Tor is about anonymous access to the internet, you can send an receive data packages, but you still have to care about whom you are communicating with and protect your confidentiality of the contained data. So Gpg4win and Tor services complement each others well.
ProtonMail (as far as I know) is a service and does not use standard compatible communication protocols for emails and files. As a service it cannot be inspected like a software product. So what I believe is that you cannot communicate with other people that use standard email crypto protocols like OpenPGP/MIME for example. So with Proton Mail you have to place much more trust in the provider compared to using Gpg4win with an email provider that support WKD/WKS like posteo.net.
Tails (as far as I know) is a live operating system, in the sense that you can start it from a removable media to reduce the abilities of attackers to place surveillance technology in the machines your are using for communications. As it is based on Debian GNU/Linux of course it does not use Gpg4win (which is the Windows port of GnuPG), but the GNU/Linux version of it. Gpg4win is there for people that have to use the Microsoft Windows system, if you are in a position to use a Free Software operating system for instance from a GNU/Linux Distribution (like Debian, Ubuntu, OpenSuse, Fedora) that has the security advantages that you can inspect it and hard it more deeply.
ProtonMail can only receive emails from other OpenPGP users, including Facebook.
You have the ability to export your public ProtonMail key, and send it to others.
However, since there’s no ability to upload/save others’ public keys, there’s currently no way to send an email to an OpenPGP recipient.