This s a really great question. I've done email marketing for multiple 7- to 8-figure companies, and here's the secret...
There ARE trigger words you can use to increase sales, and increase your results.
I love the subject line tester from Send Check It (no affiliation): https://sendcheckit.com/email-subject-line-tester. I use it myself to test for subject lines before sending, and it works very well.
I also highly recommend you make sure your tech stack is set correctly. Before you send an email, make sure your SPF, DKIM, and (maybe) DMARC are set up correctly. Your web host can help point you in the right direction. This will help make sure your email actually gets delivered! Even the best messaging in the world won't matter if you're running into delivery issues, and ISPs are cracking down on unauthenticated emails more nowadays.
For body copy/text, emulate companies that you like. What email newsletters do you subscribe? Copy them. If they're a successful business, chances are they've optimized their email copy and layout quite a bit.
After you've drafted your email, I also recommend the site mail-tester.com (again, no affiliation, I just like their tool) to make sure your email body copy isn't too spammy.
Also, I highly recommend one week later sending the email to all non-opens. We've noticed ourselves that re-sending to non-opens with a new subject line and maybe slightly adjusted copy will often result in a ~10% open rate. In other words, more traffic for a very minimal amount of effort.
Finally, the length of your email and the type of content you feature really does depend on you, your brand, and your audience. Do you LIKE writing long emails? Is your other email content long, or short? I've seen both work very well, and it's often a preference of the copywriter.
What I do think is valuable is, for a big launch, don't just rely on sending an email. We use a "content multiplication" concept where we feature a product launch EVERYWHERE — we send an email to our list, we email our friends, we run a giveaway, we post on social, we do some FB ads. The more places you can get your product to show, the better the results.
Hope that helps, and good luck.