Not a security expert just a privacy enthusiast.
There is not much of a benefit between protonmail and tutanota here because messages are coming from outside these services which means you won't be getting the encryption benefits of the message in transit. Your inbox itself is probably comparably protected between the two services so long as your password is good.
As far as mail2tor goes, you should be able to use it if desired.
Realistically you just want a fresh email address on a service that you can access in a way that can't be traced back to you for ultimate paranoid levels of security.
Proton offers an onion service, not sure about tutanota as all I can find quickly is that they planned to make one back in 2019.
I wish this place would get an onion set up, it'd address the problems we've had before of the DNS provider taking things down :/