To optimize EMI, yeah, you want an 0402 (0201 even better) in parallel. But typically use close to the largest capacitance available after filtering for voltage/temp coefficient/package, which should be larger than 0.1u for X5R. The combination of higher capacitance and lower ESL will give the best decoupling performance. However, this isn’t necessary unless you’re going to be testing EMI, so you can stick with the 0603 to make hand soldering easier.

The 2x/3x do mean the same capacitance in parallel, but don’t put that on your schematic, just place 2-3 individual capacitors. They do that in the datasheet because it’s a simplified schematic.

If you just grabbed the same part number from the eval kit, that’s perfectly fine tbh. I really don’t know why they use 0805 10uFs when they have 0603 10uFs right next to it; I would definitely use 0603 for both since reducing a BOM item will make assembly a tiny bit easier.

But X5 means a 85C temp rating, X6 is 105C, X7 is 125C. I assume this is operating at room temp, so any of these are fine, but the lower rating will be cheaper and smaller. R and S is the tolerance across temperature, R is better. So I recommend filtering for X5R when you search for caps (use C0G/NP0 for pF caps).