Since you are running your vape at 4.8 volts, I'm guessing you like a warmer vape? Unfortunately for you, it's still going to some trail and error, but maybe this can help you find a ballpark.
With your current setup, if you just dropped your build's resistance a little, like to .4 or.35, by using less wraps but same 26 ga, and vaped it to your preferred setting, your voltage would be closer to 4.0. This would give you a similar vape to what it would on a mechanical with fresh batteries.
Playing with builds on a regulated setup will allow you to tailor your builds so when you have one set ideally on the regulated at the voltage you want, you can pop it onto the mechanical and it vapes the same.
So, the one answer to NOT using tons of trial and error is Steam Engine, or any of the other similar calculators. Get the app or pop up the site and just start poking around, try some numbers and play with some coil ideas, than come back with questions on heat flux and optimal wattage, and you'll be well on your way
I build a few bellus (beli?) and I like mine at around .28-.30. I use a single battery mechanical typically, so I use good batteries. I like a warmer vape, but admittedly the batteries only last a tank before the vape starts cooling off and I switch batts.
Be aware the bellus has an adjustable pin that will screw in over usage, so using it on a hybrid style (510 pinless) is a bad idea.