I manage a landscaping company and we obviously use a ton of weed eaters and blowers, power tools etc.
Sometimes it flat out doesn't matter what you do, the tool is just a pain in the rump to start or use. We often order 10+ of the same tool, like this year we bought 10 brand new echo weed eaters, back pack blowers, and some stihl chainsaws. Every single one of those machines runs different. Each one starts it's own little weird way. Some like a bit of throttle, some flood if you give throttle. Some start with no choke, others need choke for 2-3 minutes.
They're mass-produced machines, not hand built. They're also way less adjustable than they were in years past. Basically every 2 stroke we run now has no adjustments on the carb, maybe a throttle screw, but almost nothing. If it's running bad right from the factory, I can't re-jet it, or adjust jets / airflow. My only option is to find the choke sweet spot. I blame this on every carb now being casted plastic with plastic jets that aren't removeable. Those are never going to be perfect and exact like a milled or molded metal jet in a metal carb.
Gas doesn't matter much to us. We always buy the cheapest 87, mix some seafoam in each 5gal tank, and it's good to go. Even after letting 20gals sit all winter, it's good come spring. Some machines just flat out are going to give you a hard time no-matter what you do.