It really depends on your customer. In my case, I did cold emailing. I was able to narrow down my customer by their job title/role and knew exactly who to email.
I don't really buy into gimmicks or tricks to differentiate my emails. You can read a lot of "tricks" out there, but they come across as inauthentic to me and that isn't how I wanted to establish a business relationship.
The thing I did was send very targeted emails (to people I honestly believed would benefit from my service) and every email was personalized (and I don't mean using a template and swapping out variables). I sent each and every email from scratch, one at a time.
I did read a few books on sales outreach and prospecting ("Predictable Revenue" and "Predictable Prospecting"). They were helpful and I did pick up a few ideas from them, but I mainly took the knowledge and paved my own prospecting/outreach strategy from it.
With that being said, I haven't done any outreach in over three years. All of my customers come to me, mainly referred to my service by existing customers. Or customers that leave a company and advocate for my service at their new company.