To answer the first question, yes you can install 4 m.2 SSD's with card to this motherboard. From what I know, you may use all of these SSD's without RAID setup for Windows. You may install Windows on whichever SSD you select during the Windows installation process. They will be displayed as a single device once you also setup using Computer Management.
Now for the following setup question, it's achievable. Once you have this setup, all you have to do change the PCIE settings for the cards slots inside the BIOS to RAID.