Do negative modifiers change a critical hit? [duplicate]

I want to play a champion fighter and am considering whether or not to get the Great Weapon Master Feat which states:

Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a – 5 penalty to the attack roll. If the attack hits, you add +10 to the attackā€™s damage.

If I take the -5 to attack roll and roll a critical hit, will that crit still be in effect, or will the -5 counteract that? Also, in the event that I do crit with a -5, would I add the +10 damage before, or after I double damage, like with other modifiers. It doesn’t say that the +10 is a modifier specifically, so I was a bit confused (note: for critical hits, my group usually has house-rule to double the damage and then add modifiers instead of the normal double dice.)