Thank you both!
Its my own mistake for not reading up enough on this.
Short plain answer for others who might have the same idea I had.. when using the array you have paritiy drive(s). SSD`s does not work well with that and should be avoided.
New plan is to use the 2x Samsung SATA SSD`s as pool devices either mirrored or by themselves. Not decided yet.
Use the 500 GB NVMe drive also as a pool device but working as a cache for 2x 2.5 inch 5400 RPM 1 TB wd spinning drives. Those should be low power usage and silent. I assume they will sleep most of the time apart from when the mover is working and if I access data on them.
Got plenty of new drives like that from new customer laptop`s I have sold that got replaced with SSD`s a couple years back.
This setup should give me the "full" Unraid experience to test out things in a reliable way and I expand on it as I see fit.
Not sure if I should use ZFS or BTRFS on the pool devices though, I read in forums that some went back to BTRFS from ZFS after some issues.
I also read some use ZFS on one drive in array to get access to snapshots.
Any big mistakes in this setup or does this seem ok?