Truenas scale hardware suggestions

I am currently running Truenas scale on a hp dl380 gen9 with 10x3tb drives in a raidz2. I was using truecharts, but obviously that isnt happening anymore.

I have been slowly buying stuff to make a different nas. The new server will be for file hosting and plex, and the hp server will be for vms and possibly docker. I have bought 2x16tb drives, server chassis, lsi 9300 16i, and 10Gb nics for p2p file transfers between servers/computer.

I was planning on using a 9700k, asus z390-a, and non ecc ram that i already had laying around. When i brought this plan up to a friend that works in the field, he highly discouraged me from using non ecc ram.

I do have a 5800x system that i could possibly use, which i would have to buy udimm ecc ram for. I wanted to use the 9700k for plex transcoding, but if ecc ram is a dealbreaker, i will have to change plans.

The plan was to throw 4 or 5 16tb drives in the new system, and run them in raidz2. If needed, i could expand the pool later on. I thought isolating vms/containers and my storage would be the ideal solution.

Should i change plans, and move over to the 5800x system with ecc ram?
If i do switch to the 5800x system, how much ecc ram should i be buying for the 4/5x16tb drives?