I've done a lot of that route numerous times. The portion from Hope to Princeton is one of my favourite rides in B.C.
Traffic isn't bad and the motorists on Highway 3 tend to give you some room when they pass you.
Allison Pass is a long climb with a lot of elevation gain. There's a rest area at the Hope Slide, after you've done something like 16 kilometres of tough riding from Hope. There are other stops and picnic areas along the way.
From the Hope Slide, it's fairly good riding for the next while, but later you'll get another big climb to the summit.
The elevation gain between Hope and the summit is more than 1,300 metres. Expect to go slowly.
There are no stores or services from Hope until you reach the Manning Park Lodge, 10 kilometres past the summit. At the lodge, there's a restaurant and a small convenience and grocery store. There's also a fountain and water tap.
When I do this ride, I normally camp in the eastern part of Manning Park. The Mule Deer camping area usually has a spot for the night. It doesn't fill up nearly as fast as the camping areas closer to the summit.
There's a gas station, store and restaurant just past the east gate of the park. If you're leaving the park first thing in the morning, it probably won't be open. Don't count on it.
To reach Sunday Summit, you'll encounter one short but nasty climb. It's around eight kilometres of agony. But once you reach the brake check at the summit, it's mostly flat or downhill to Princeton.
Along Highway 3, there are a number of camping areas between Princeton and Keremeos. The road here does not have the mammoth climbs you'll encounter on Allison Pass and Sunday Summit.
I live north of Penticton, so I haven't done the portion from Keremeos to Osoyoos.