We visited here on a Wednesday in early January 2023. The weather was perfect- sunny and warm. When our tour bus first arrived at 11 am, we were told that there were no ships arriving to pass through the locks until 2 pm.
So, first tip- check when a ship will be going through, otherwise it would be a disappointing visit here.
We came back at about 1:50 pm and the place was very crowded with spectators to watch a Holland cruise ship Zandamm pass. We did see the Miraflores locks open to allow the passage of the ship. Simultaneously, in the the new locks that are larger than Panamax south of Miraflores, we could see that an even larger cruise ship was passing through.
One issue is that the cost of watching this is a bit exorbitant at over $16 USD per person. You cannot just see the Miraflores Locks, you are also given a ticket to an IMAX film about the Panama Canal's history.