I wouldn’t worry about a different mix design unless the parking lot needs to be open in a short amount of time, if it does I would just throw in some fast dry additive but talk to your manufacturer to see what they suggest. Make sure you add it in the cost if you do have to run an additive as it’s not cheap!

Watch the weather not only in the short term but down the road up to a month. Regardless of the sealer or additives, if it freezes within a month, it’s likely going to fail.

Usually additives and cut down the water. There are some additives that will help push out the water once the sealer is placed. I think it’s called Zytec or something. Most latex additives just bulk up the sealer. Use caution when adding sand, it can be similar to adding too much water. You can only stretch the binder so much. I always advise people to consult with their manufacture on altering mix designs.