Gmail offers imap amd smtp access. You have to enable 2FA, and then it will allow you to create account for so called “less secure apps”.
In your place, I’d either continue using gmail directly, or finish the configuration of the self hosted mail server and just use that with any smtp/imap client. I suggest getting a separate domain for testing first, before moving your primary inbox there.
That’s not a slow laptop. I’ve been daily driving worse for years.
To protect the data from random thief just browsing through the files I still use ecryptfs. It only encrypts the home directory, and the keys are derived from my accounts password, so no extra hassle.
The encryption is weak by the current standards, and wouldn’t stop a determined attacker, but it’s 100% better than nothing, and I’ve never noticed any performance problems.