Can't say what screws they are, but removing the drives for every bios update is asking for component failure. Sounds like you're scared of data loss? As in sooner or later you might drop one, or one of the gold contacts will get damage (on the drive or the port),... If they're installed, leave them in there. The bios will loose the raid configuration whether they are installed or not. That's the ONLY thing it will lose, the raid configuration. YOU WILL NOT LOSE ANY DATA THATS ACTUALLY ON THE DRIVE.
You'll only have to recreate the array and everything should boot up immediately.
Nope sorry, i don't use raid for among other reasons, precisely the problem you're having. One of the other reasons is that a single nvme drive alone (especially the likes of a 970 pro like you're using) is capable of maxing out the pci-e lane throughput allowed. See if this video is of any help. One of my fav youtubers. It isn't exactly the same board or platform, but it may give you an idea. (on why raid on an nvme is just plain pointless) https://www.youtube.com/watch?v=z_wjktb1wP4
From what i recall its something like
1. Disable CSM in bios
2. Enable raid support in bios
3. then assign the drives to the array
4. then actually create the raid
Could also see if the easy tuning wizard is of assistance https://dlcdnets.asus.com/pub/ASUS/mb/LGA1151/ROG_MAXIMUS_XI_CODE/E14941_ROG_MAXIMUS_XI_CODE_UM_V3_W... (page 3-11) of your manual or this specific Asus Raid Configuration Guide for your board https://dlcdnets.asus.com/pub/ASUS/mb/LGA1151/ROG_MAXIMUS_XI_EXTREME/E14794_RAID_Configuration_Guide...
When you've manage to succesfully set the bios settings and recreate the array, windows should just boot. Maybe all this hassle will convince you it's not worth the pain, because you'll have to do it EVERY SINGLE TIME you update your bios