My setup is 2x NVMe SSDs and a single large SATA HDD. Archive and backup is 4 bay DAS (RAID5) and 4 bay JBOD.
NVMe
NVMe
I just have both the media cache and scratch disk on D: NVMe SSD. And effectively avoid using scratch disk by having a large amount of RAM (128GB). More RAM is always better than scratch disk on fast SSD.
Once the file is loaded for editing, it just sits in RAM - so speed of loading/saving is determined by choice of NVMe or SATA. Up to you and the size of your typical media files. But SATA SSD still better than HDD. Loading and saving large media files can saturate SATA interface (500MB/s), but HDDs usually hit 180-250MB/s max.
I actually work off HDD with archives, but deadline jobs I would create a LR catalog and session on working SSD - then archive to HDD after deliverables are sent to the client.
Have 3 backups of your master archive. I have 1x onsite mirror, 1x onsite differential, and 1x offsite.