I have seen quite a few indications in several posts that "your equipment may change", however, this has not been my experience so far (ie. I book PTY-IAD/BWI on a Max 9 and always get the equipment I booked).

I am starting more travel to South America where Copa makes more sense schedule wise but want to get a sense of how often these equipment changes happen, particularly from Max 9 to non-dreams equipment.

My alternative is flying Delta to GRU/EZE/SCL where I can have either Delta One Suites or at a minimum Delta One and then connect to LATAM if needed, but this makes my trip longer.