i just don't like the po gift they offer this time. still going to get the phone. 

Better apply clearpex 1st

No worries Bro. I was previously an S7E user myself that just recently retired the fantastic phone for it's 3.5 years of service. To answer your questions :

a) The experience that I have with the pre installed screen protector on my S10+ is pretty good. I worked flawlessly in protecting the screen from scratches but doubt when it comes to falls. For that you would need a TG SP like Whitestone or Tmax.

b) Had the same experience trying to fit the TG SP on my S7E, in the end, I settled for the X-one screen protector and it lasted me till today. From my experience using the Tmax TG SP, it works well with majority of casing.

c) I also was tried using my S7E under water in the pool to snap pictures and record videos when I first started using it. Luckily mine didn't encounter any issues except for the weak speakers due to being submerged in water. Was back to normal, once it dried up. So, in general I would say best to keep away from submerging your phone in water unless it is a pure accident.

Got free casing inside bro?

nope. don't have any. my eta delivery is tomorrow.

so the free case is jelly type like note 9 or hard case like s10?