Protip: you can easily sync obsidian by sharing the top-level vault directory with syncthing. Its entirely transparent, you just start obsidian and open the vault, and changes you make on one system automatically appear on others.

As for protonmail, its better than google -- but you're right in the data ownership. In the case of protonmail, they have a much better track record than Google, but if you are really paranoid choose a service that supports SMTP/SNMP. You can then just have a mail client store the mail as an archive or connect it to any other mail system.

I have mentioned my preferences before, but I'll refrain from turning this comment into an unpaid ad. Drew Devault's recommendations are pretty good though: https://drewdevault.com/2020/06/19/Mail-service-provider-rec...