Lavoslav

Guys, thank you very much for replies. You've broken me out of my "thought loop" so to speak and given me great pointers how to proceed. 
 
@bmartino1
Tyvm for the screenshot of your main tab and the writeup. Helped greatly to visualise things better.
As for 3-2-1- backup, I am set for my needs, though I don't do the last part of 3-2-1 offsite but rather have a solution where I monthly copy stuff I need on disks I keep safely stored and not used in any other way.
 
@Vr2Io
As far as power protection goes setup is as follows:
UnRaid - 1500VA ups, set to poweroff server if it hits 5 minutes runtime capacity.
Backup machine - 650VA UPS. Backup machine is low powered QNAP (not using their terrible OS though). Almost always turned off. Wakes on Lan when backup needs to run and powers down when done. Set to poweroff at 2 minutes remaining runtime.
Bare metal and TV - 1000VA, run untill dry, which is never since they are turned on only when in use.
POE capable switch, POE powered AP and POE cameras (powered through switch) and Modem, have it's own 1500VA, they run untill dry
 
I both love you and hate you for saying "...how you define pool / array is main / backup. For me, I use array as backup tier,..", I've never thought abut this in a way you framed it. For me it was all on the array except NVMe directly passed to VMs. That sentence, combined with bmartino1's suggestion, solved it for me.
 
As far as disk setup goes I'm gonna go very close to what @bmartino1 wrote in second post. For now 2 of the 3TB drives are gona go into array as xfs and third will go in array as zfs for replication, but I'll get 3 more larger drives at some later date for a second ZFS pool since @Vr2Io gave me some food for thought. 
 
Unraid array
- party
1x WD Blue 4TB
- array
2x WD Blue 3TB, as xfs
1x WD Blue 3TB, as ZFS
1x Toshiba 2TB, as xfs
 
Cache disk
1x SanDisk Extreme Pro - 500 GB, as ZFS
 
ZFS Pool raidz1 HDD
3x Seagate 16TB Segate Exos
 
NVMe disks direct pass through to VM's
 
Future expansion another ZFS raidz1 3 disk pool.
 
Marking this as solved, but if anybody has anything to add or point out, feel free. Parhaps it can help somebody else in similar situation.