M.2 Slots

Hello! I have a question. I got a mobo and that is B550M mortar. Is that ok to occupy my 2 M.2 slot not USING THE PCIE SLOT. One is for OS with a 120gb nvme and the other slot is for apps/games with a 1tb nvme. Also is it ok to swap them? the 120gb with os is at the slower m.2 slot(lowerpart)...

This is a good pc to play Fortnite at 144fps all in low and res 4: 3. I'm thinking of also buying a 144hz monitor. Is a good choice? Thanks for all the reviews. CPU : AMD Ryzen 5 2600 Hexa-Core, 3.4GHz w/ Turbo to 3.9GHz, 19MB Cache MOBO : Micro-ATX MSI B450M PRO-VDH GPU : MSI GeForce GTX...