With a SOC like that, that no way will only serve as a NAS, i can see my self easily hosting a dozen container on it and a couple VMs. That said, 12Gb is quite sufficient for my need.
You definitely want an 8th gen (Intel) or better to have Jellyfin Quick Sync support. It's what I have (i5-8400T) and it offer a fairly decent AVC (h264) and HEVC (h265) transcoding for my usage. However, for futur proofing consider an 11th gen for the AV1 support.
For Jellyfin, dont get any lower than 8th gen if you want to transcod using quick sync. And if i correctly remember, you will nee 10th gen or higher for 10bit transcoding.
I'm containerizing everything, I like to keep my setup simple, no OS containerizing since I will be using a low power minipc (NUC, Hp mini, dell micro or lenovo tiny), I will use proxmox in the VM to get an idea on how it works and because I think the web UI might be easier to use than SSHing to the VM. Later on the new server I will mostly use debain+docker.
With a SOC like that, that no way will only serve as a NAS, i can see my self easily hosting a dozen container on it and a couple VMs. That said, 12Gb is quite sufficient for my need.