The screws all have a bit of threadlocker on them, so the first time you undo them it’ll be a little difficult. You should always use a screwdriver that fits, not a bigger or smaller one–bigger or smaller is irrelevant to your ability to apply maximum torque without stripping the head, it must fit!
If you have already stripped a screw head, or partially stripped one, you can use some sort of abrasive paste to give you a little extra grip (something like a rough polishing compound, toothpaste, maybe baking soda with a tiny bit of water).
I know having phillips head screws is thought by some to send a signal that the manufacturer supports users being involved with their hardware, etc–but I think it’s a poor choice for a fastener that size. Maybe use torx and include a $0.20 driver with the $1500.00 computer?
Also, please include a few extra screws–they’re small, easy to lose, and hard to find
Also, the holes the screws go through in the aluminum back piece on the 15v3 are too big. I’ve had at least one screw head pull entirely through.