I did 8-12 grafts on 2 trees. A pristine worked to trailman, and a droptine worked to kerr. IF one fails I got plenty of backups. And the next year or two, I have a bnch of maturing laterals. The grafted leader dies, you might be able to use a lateral for the leader. The tree might be wanting to use it anyways.
Cant speak with much of any experience, but my crabapple grafts seem to be growing faster than orchard apple varieties.
Some might be better in general. Trailman and kerr have been rockets. easily 18 inches so far.
Tounge and whip grafts grow better than cleft grafts. Sometimes you gott do cleft on larger branches. My topworks are are 2 years old bareroots, maybe 7ft tall pre topwork pruning.
I wonder if replant disease sensitive rootstocks should just be put in the ground as-is to reduce year 1-2 strees and begin growing helathier, then topworked. Instead of the usual graft n plant.
My failed graft anotonovka's at camp are monsters compared to the same failed graft ones I regrafted the same spring. I may topwork them, I may not. A plain old antonovka makes a decent september putting on weight for deer apple. Especially compared to what up in birch n maple wastlelland there......