"Pitch and Putt", just like "Par", depends on the intended player. That's why I keep lobbying for the accurate use of "Par Two", rather than calling a hole a "must get". If a 970 rated player played the hole, and knew beyond a shadow of a doubt that he might drop out of cash if he took a three, then that's a par two for the 'Gold" level player. That might differ at each skill level. It's why I sometimes list different color "tees" for my local, single tee courses here, and tweak the par 'correctly' for that skill level.
For touring pros, any open (no significant obstacles) hole w/ no serious OB under, say, 400' (counting in relative elevation)... is a pitch and putt hole. For an 850 to 935 rated player, that might drop to 200' to 250' max.