Besides cringing at my writing and experimenting with structures, I also look at data while updating welcome email.
I am aware visitors signed up for my newsletter to read content, so why make them wait until I publish the next issue?
So I have this "Top performing essays" section in a 200-ish word welcome email. I add 3-5 of my best works that I know will instantly build trust and authority with my readers.
Every 45 days or so, I look at the clicks on each of these recommendations and replace 1-2 of them with my recent works.
Replies are another factor I consider in recs. More than opens and clicks, replies are my North Star performance metric. On average, I get five replies each time I publish. If the replies are > 10 on any issue, it gets into the welcome email soon.
Small steps, Big impact.