I highly recommend Qubes OS for its compartmentalization and its ability to be stateless. It has the ability to route all traffic over TOR as well as a VPN. It is meant for laptops primarily, but can work with some desktop boards. It is hit or miss still.

https://www.qubes-os.org/

I really like the idea behind the stateless computing from the Qubes creator.

https://blog.invisiblethings.org/papers/2015/state_harmful.pdf

At a minimum I would recommend full disk encryption with Veracrypt - https://veracrypt.codeplex.com/ - or something similar. If someone were to try to plant evidence on your computer, you at least have the encryption to protect you at rest.

To protect you while browsing, I recommend to at least use a VPN - https://www.privateinternetaccess.com/ (you can buy a gift card with cash and use it to pay for the service) - if not use the TOR browser, for all research. -https://www.torproject.org/projects/torbrowser.html.en

Not sure which browsers are still affected, but don't forget about the STUN server request that can reveal your IP even if using VPN. The following is a link to test for the ip leak.

https://diafygi.github.io/webrtc-ips/