Back from my trip.
As 1vertical just noted, in YNP we did stay in guest/park_employee housing and it was not primitive at all. Price was $25 per night per bedroom and we could do all our own cooking in a modern kitchen. We made breakfasts and dinners, but for lunches we simply snacked in the car or out on the trail..
We did hikes in GTNP including the Jenny Lake, Inspiration Point, that Moose loop, and many others. Grand Tetons is about hiking and not so much wildlife viewing, but we saw bears, moose, elk, bison, pronghorn, mule deer, and birds.
YNP is more about a driving safari for wildlife viewing and geysers. Contrary to what was previously posted, the distance from the Lake Village area to Old Faithful is only 38 miles and takes less than an hour (we drove it 5 times). We drove on almost all the open main roads including the entire Grand Loop. We visited all the Visitor Centers and Information Centers and went in/out both the Northeast entrance and the South Entrance. We did not go to the East nor the West Entrances. We were near the North Entrance when we visited the Mammoth Hot Springs area (VC has free WiFi), but did not pass through though we were told the Arch was open.
We saw bison, elk, bears, bighorn sheep, pronghorn, mule deer, a wolf viewing pack, birds, and Homo sapiens.
We learned that less than 5% of YNP visitors really get out of their cars and hike. About 95% will drive from spot to spot and just look from the car window or get out to view an overlook.
Here is my BIG TIP though: When driving to view wildlife there is always something better around the next turn or over the next hill. At first, we would see a herd of bison say a quarter mile off the road. Lots of cars would stop and people would get out to take photos. But we would drive a half mile and another group of bison would be in the road, so within 5 yards of your car. So our method was to be discriminating on stops for photo ops and to drive through "animal jams" where the animals were 100 yards or more away from the road. For closer animals, we would often drive through and loop back, then reverse direction. That way, we went past close-up wildlife up to three times. We had plenty of time to do this because we started early each day and lived in a central location.
As for geyser viewing, I think most park visitors miss most of the spectacular geysers because they don't run on schedule like Old Faithful and require walking or more driving to get to them. The park rangers sometimes know when some geysers will go off from what has happened in the past week, but they can only estimate within an hour or two. We saw geysers go off that some park employees had not seen themselves in over 8 years of working in the park. Patience, time, and luck play a part in all this.
I will post some photos later today.