For your requirements (which are like mine), Grizzly RV park in West Yellowstone and the Virginian in Jackson. Both have full hookups including WIFI. And both towns have real grocery stores. Expensive, but not nearly as bad as in the park, and you have choices.
And everything is a long drive. One lap of the grand loop in YNP is 140 slow miles. And its made slower by "Buffalo Jams". When the bison want to cross the road, they cross the road. DO NOT try to drive thru them. Their huge heads house a brain the size of a pea. The rest is thick bone. I have a picture somewhere of a young lady complaining to a trooper next to her severely dented car door. Hard to give a traffic ticket to a bison. (No pockets).