Quick sanity check windows installs M.2 drives in Post IDE world

[True]

Ok this is a stupid question but i have never had to deal with this isue before and I am 99% sure how windows will act but i want to make sure before i lose data.

 

My pc has 2 m.2 slots the 3.0 one current has my sata SSD in it and is my windows drive and in the only drive in the system..

 

I just bought a 4.0  WD sn850x  SSD  I plan to stick it in my 4.0 slot.     

 

If i power down pc Put in the drive Boot to a windows installer USB and pick the new drive as my target  Will my system now defult to booking it and not my sata..    I wanted to avoid having to backing 1.3 TB of stuff on that drive and just do a drive to drive move then reformat it as a data drive after.      Since we are no longer in a IDE world there is no hardware master drive or stata drive order with a NVME m.2 drive invloved.      

 

I just want to do a quick sanity check before i do this if i can save the backup  (All my Important data is already clound backed up automaticly so the only real point is my steam games and similar)