The verdict

Plex
Nvidia RTX 4000 SFF Ada transcodes more streams (~45 vs ~20).
Local AI
Nvidia RTX 4000 SFF Ada has more VRAM (20GB vs 16GB) - up to ~20B (Q4).
Fit
Nvidia RTX 4000 SFF Ada is easier to add to a mini-PC (low-profile PCIe).

Which wins for each job

Job Intel Arc A770 16GB Nvidia RTX 4000 SFF Ada
Plex transcode ~20 streams ~45 streams win
Frigate NVR ~25 cameras ~25 cameras
Local LLM 16GB VRAM 20GB VRAM win
Fits a mini-PC full-size PCIe, DIY build low-profile PCIe win

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 Intel Arc A770 16GB Nvidia RTX 4000 SFF Ada
Price (list) $330 $1,250
Type gpu gpu
Interface pcie pcie
Transcode H.264/HEVC/AV1 encode (Arc) H.264/HEVC/AV1 encode (NVENC Ada)
Frigate detector OpenVINO TensorRT
TOPS - -
VRAM (GB) 16 20
Low profile no yes
GPU sharing - vgpu
Power (W) 225 70