hey dan!
we have a thread somewhere, with different config for different relays. I do have Amazon SES in place at a few servers, so I can asure that it works. however, depending in the service you use, you might need to validate your domains and more - esp ses is complex on that, so I understand if it’s not your first choice 
if I find the thread, I’ll link it… however if I remember right it was pretty much straightforward from the ses for exim docs, so I think that should work for other services as well.
edit: here you go How to configure HestiaCP / Exim 4 for SMTP Relay (SendGrid, Mailgun, Amazon SES, etc)
PS: basically much less than what you all have - just an authenticator, a router and a transport…