On the power side, running your boards off a high quality 90W brick is reasonable. The medical-grade 90W Meanwell brick Intellijel sells would be a good choice. I can tell you from experience, there are a lot of terrible no-name power supplies that won’t deliver on their specs or fail when you need them most.
From the shape of your case, I’d put the boards directly under the top row—it looks like there’s a ton of room there. As opposed to the bottom row, where every extra mm counts.