I don’t have any long term experience, but I have played dozens of combos up to the mid teens on both BFA and private servers to get an idea of what classic pairings might be like. I found it easier to play 2 characters than 3. If 3, I’d go for a full 5 and buy ISBoxer.

Warrior/Sham driving from the warrior works pretty well.
Druid priest lock works pretty well when they’re all in caster form, and gives you the flexibility to have a tank later.