We have never used FP for F! But we usually do a dining package. 2 years ago in March we didn't use anything and had perfectly fine seating about 30 minutes prior.
I can't say if you need a F! Fastpass, but, since adding the third track, wait times for TSMM were minimal. I think the longest we waited during our June trip was 30 minutes, but usually it was around 15.
We've done Fantasmic many times and have never used a FP, we did the meal thing with Brown Derby once, otherwise we just do stand by and have had plenty of luck.