I've got the following
C - Samsung 980 PRO - OS. 500GB (nvme m.2 pcie 4)
D - Sabrent M2 - Games. 2TB (Sabrent rocket nvme m.2 pcie 3)
E - Samsung EVO - OS IMAGE. 120GB (EVO 850 SATA)
F - Samsung EVO - Software, Docs. 250GB (EVO 850 SATA)
G - Samsung EVO - OS clone. 500GB (EVO 850 SATA)
Macrium OS clone from C > G comes in very useful. I used to use Windows backup and restore to create a system image, but this screwed me over once as I restored a corrupt image.
Once the OS clone is complete I should really disconnect the drive but never do as its a faff.
A 500GB OS close takes 3 mins 15 even to the old EVO 850 SATA drive, though drive is only 70GB full
I would highly recommend having a seperate OS to games drive then backup stuff.
External wise, I also
2 TB Samsung portable SSD T7
1 TB mechanical WD Mybook with photos on
1 TB WD drive which I've had for years connected to a WDHD TV