I don’t like using “encrypted” email because in fact email is really not a secure protocol by default, you can send secure email to each other but if you’re communicating to gmail, yahoo, outlook… You will lost all your privacy. Hosting an email service is good but do not use encryption when talking randomly to gmail accounts.
1 - Maybe try to use https://duck.ai it’s open source model hosted by duckduckgo
2 - Element is not the way to go for sensitive infos, it’s like a discord replacement in the way of joining public groups, not really a good messenger for really secure and bulletproof 1:1, recommanding Signal or even better SimpleX
4 - Use Mullvad.
Seen a lot of different opinion in this, but personnaly I would recommended this.
SimpleX, for the most privacy (but not really appropriate here) Wouldn’t use any of threema wire and else, as it’s not the best.
A good option in the case of this project is a matrix server, if the group is public it’s the best thing. Try to host it somewhere else than matrix.org. Will have no real hiding but surely anonymously if done correctly
You will always find problems associated with every thing but here’s some recommandations :
For a good start, Signal and his forks (molly…)
For daily basis and better than Signal, choose SimpleX (SimpleX is only feature incomplete for the mainstream app, but in it you can send texts, voices, photos, videos, live messages, have a PP, a alias for your contacts…)
Important stuff and activism, use Briar
Mobile is not safe in any kind (instead maybe Linux phones, without mobile network)