For best route, I would suggest google maps. For places to stop, if you are going in on I40, I would recommend getting as far as you can on the first day, so you have time to stop at Petrified Forest National Park on the second day. The north entrance is essentially on the highway, which more or less cuts across the middle of the park. The main road through the park goes north, then loops back south to eventually dump you out at the south entrance. From there, it is a short drive back to Holbrook and the highway. The first part of the drive is mainly viewpoints, but once you cross under the highway you get to places where you can hike. I would definitely recommend the trail at Blue Mesa. The landscape there is otherworldly. There are visitor centers at both entrances. You can see quite a lot in just a few hours.
From PFNP, it is a short drive to Meteor Crater, and then another short drive to Flagstaff, then another short drive to Sedona. The drive from Flag. to Sedona is only about 41 miles, but it takes more than an hour as the road drops into a canyon and gets pretty curvy. Right before the road descends into the canyon, you will pass a place on the left side that is like a roadside park/rest stop. The city allows local Native Americans to set up a table to sell their handmade jewelry and other items. Well worth a stop for a few minutes, as the jewelry is quite nice, and priced extremely well. They are quite friendly too. There are restrooms there too, but they have been closed for the entirety of the pandemic, so not likely to be open when you get there.
There are a lot of places to hike around Sedona, so do your research before you go. You will need to find out where you can buy permits and the like. If the weather is clear, you can go up to the small mesa above the city and where the airport is situated and watch the sunset. IIRC there is a restaurant and a bar up there, along with a hotel.
One restaurant we really liked is on the other side of the main road where it intersects with Airport Drive. I think it is called Judy's Restaurant. It is a small restaurant with a cozy interior, good food, and good service.
If you decide to get away from Sedona, you could go SE to Jerome, which is a revitalized mining town in the mountains. I wouldn't go there just to see Jerome, but it is definitely worth a stop for an hour or two if you happen to be driving by.
North of Sedona is of course Flag and the Grand Canyon. If you decide to do GCNP, you have to go through the main (south) entrance. The road to the east entrance is on Navajo land, and is therefore closed due to Covid precautions. If you want to just see the canyon, you could do it fairly easily as a one-day trip from Sedona.
Flagstaff has a nice little downtown area. Unfortunately, the sites of interest around Flagstaff such as Lowell Observatory and the Museum of Northern AZ are closed. If you decide to stay the night in downtown Flag, do NOT stay at the Roadway Inn, even though it has a very convenient location. For outdoor equipment/clothes, we liked Peace Surplus on Bus. 40/Hwy 66 on the edge of the downtown area, and Babbit's right next to the square. Both have very friendly staff.
One place I would *highly* recommend for a meal on I40 is the train station/hotel in Winslow, just one block from the main part of downtown (if you could call it that given Winslow's size). This is one of the historic Harvey House hotels, built in the late 20's. The restaurant there, called The Turquoise Room, is fantastic. It is hard to believe while you are driving through Winslow that there could be a restaurant that nice in the vicinity. And the food is reasonably priced too. And too, even if you aren't hungry, the place is still worth a stop if just to explore and stretch your legs. The place is easy to find - Winslow is pretty small. You could do PFNP in the morning, then get a late lunch at the Turquoise Room, and then drive in to Sedona. Of course that depends on where you spend the night in New Mexico.
C