Hi Angie,
It's lovely to see a question from an international traveller like me!
I would plan to visit Hollywood Studios on a day when there are no Extra Magic Hours available for Guests staying at the Disney Resort hotels. We have always found that this increases the amount of Guests who choose to visit any of the theme parks on those particular days.
With the water parks, I would simply avoid the weekends as Saturday & Sunday always seem to attract more locals than during the week.
As to which of the two water parks to visit, that is a tough decision as my family love both of them but, I have to say that Typhoon Lagoon just has the edge for us mainly down to the wave pool which we all really enjoy.
You can find out more about what is on offer at Typhoon Lagoon
HERE & Blizzard Beach
HERE which may help you to make your mind up.
Wishing you a magical trip!