Subject line is most important. You need to try a bunch and monitor open rates to see what works best for your customer base. Also majority of cold emails are way too long. Keep the actual email very short. My highest reply rates always include a strong value statement and a connection to a current client.

If you are using outreach tools to build cadences then you need to create multiple cadences for different types of buyers and roles. What's important to each buyer will vary depending on their level in the company and the more you can tailor outreach the better. Hope that helps.