Some people never drain the tank over the winter - or for the 4 years it sits in their generators....and never have a problem with the gas from their local stations . And for most of America that is the E10 - ethanol mix.
In 25 yrs I've never drained a mower's tank. Many of those years with E10 in the tank. The mower ran just fine afterwards.
We don't have ethanol free pumps around here. The very large dealer in town, all brands of machines, Ducati's on down to Kymco's....jet skis, 4 wheelers, etc., etc. fill the tank in your new vehicle with Shell E10 87 or 93, from down the street, depending on the manual.
What gas?....
Whatever you think is best.
But, I'd always recommend (as does the service desk at above dealership) that one use gas listed on the pump as a Top Tier fuel. They don't cost a penny more.
They are blended to keep modern engines healthy and running cleaner.
Stig