The verdict

CPU
GMKtec NucBox M5 Plus has 3.4x the CPU throughput (17,851 vs 5,307 PassMark).
Plex
Ugreen NASync DXP2800 transcodes more 4K HDR streams (~5 vs ~3).
Idle power
GMKtec NucBox M5 Plus idles lower (9W vs 10W) - cheaper to run 24/7.
Networking
GMKtec NucBox M5 Plus has more NICs (2 vs 1) - better for a firewall or VLAN trunk.
RAM ceiling
GMKtec NucBox M5 Plus takes more RAM (64GB vs 16GB).

Which wins for each job

Job GMKtec NucBox M5 Plus Ugreen NASync DXP2800
Plex / Jellyfin ~3 streams ~5 streams win
Frigate NVR add a detector ~4 cameras win
Proxmox / VMs 17,851 PassMark win 5,307 PassMark
Firewall / router 2 NICs win 1 NICs
Local AI / LLM no slot no slot

Approximate - capacity estimates from curated specs, the same logic as the recommender. Verify against your exact setup. Prices move; check the retailer.

Full specs

Spec GMKtec NucBox M5 Plus Ugreen NASync DXP2800
Price (list) $299 $299
CPU AMD Ryzen 7 5825U Intel Processor N100
Cores / threads 8 4
PassMark 17,851 5,307
iGPU Radeon Vega 8 Intel UHD (24 EU)
NICs 2 1
NIC model Realtek 2.5GbE Intel I226-V
RAM max (GB) 64 16
M.2 free 1 2
PCIe slot none none
Idle (W) 9 10
TDP (W) 28 6