I expect it’s going to be crowded the whole time. There is zero park availability at Disney World that week (for March 13-19).
(This is also spring break for our area in Tennessee- it’s true that not every school has spring break that week, but there are a significant chunk that do.)
I just looked at hotel availability at Universal- zero availability for March 13-17. (Their reservation system is somewhat wonky, so maybe there are other packages available.)
I would expect each park hits “capacity” every day, probably relatively early. Parks are open 8 am-10 pm, with early entry for hotel guests at 7 am for both parks.