If you have sensitive information you don't want prying eyes to see, you shouldn't be using email to being with. You're options are, not sending it, Signal/Molly, or SimpleX. Briar might be the only other option if you use a vpn when accessing it.
The crux to this whole debate is email is inherently not as secure as other mediums of communication transports.
I'll stress this point, so as not to leave room for debate. If your threat model is needing high privacy, email is not the form of communication you should use. The privacy you should shoot for with email is privacy from spam and companies selling out your email.
The best use case for email privacy I would go for is aliases to protect my main email from unwanted communications from marketing, phishing, or scams. As well as email account security from hackers. If you want privacy from the email company itself and government don't use email.