1.) Depends on your skill level. You'll want ankle strength and skate mileage before diving into a super stiff pair of skates. Since you're used to using softer skates, you may find the stiffness not to your liking and/or overwhelming. As such, I'd recommend a pair of mid-level skates. Not too stiff, not too soft, like a s180 or perhaps s190 if you want something a little stiffer. Going from a s160 to a 2S is a large jump in stiffness and I personally wouldn't recommend it. A good indicator that you'll want to move up to a higher tier of boot is if the boot prematurely breaks down (within 1-6 months). Take this fictional scenario into account: "I'm used to using an intermediate 67 flex, but several people said my shot will improve if I move up to a stiffer flex. I'm thinking about using a 112 flex, do you guys think that's a good idea?"
2.) If you find that the Supreme line of skates fit your needs: Fit, comfort, and durability, then I see no reason to go custom. For me, the custom skate has always been more about stepping on the ice and not remembering I'm in a pair of skates (fit and comfort), but rather I'm in the moment, playing the game. That's been my indicator for gear. If it's working and it's working well, I'll never even notice it. If it's not working, then it becomes center stage and the gameplay takes a seat in the audience. Unfortunately, for me, the latter was what I felt and experienced when I went with retail skates. Here's the reason why I went custom. If your dogs are barkin' every time you step on or off the ice, then you can try boot stretching/punching, and if that doesn't work, then you can try a different brand/model AND if that doesn't work, go custom.
Also, never buy off-the-shelf or pro-return custom skates. That includes Bauer and CCM. The boots were made for that particular player's feet. And unless you're lucky enough to have the exact same left and right foot dimensions as them, stick with retail or get your own custom set.