The verdict

Plex
Intel Arc iGPU (Core Ultra) transcodes video; Intel AI Boost NPU (Core Ultra 100) is detection-only (no transcode).
Frigate
Intel Arc iGPU (Core Ultra) handles more cameras (~25 vs ~13).

Which wins for each job

Job Intel Arc iGPU (Core Ultra) Intel AI Boost NPU (Core Ultra 100)
Plex transcode ~8 streams win none
Frigate NVR ~25 cameras win ~13 cameras
Local LLM none none
Fits a mini-PC built into a CPU built into a CPU

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 iGPU (Core Ultra) Intel AI Boost NPU (Core Ultra 100)
Price (list) - -
Type igpu npu
Interface built-in built-in
Transcode H.264/HEVC/AV1 encode -
Frigate detector OpenVINO OpenVINO
TOPS - 11
VRAM (GB) - -
Low profile no no
GPU sharing sr-iov -
Power (W) 0 0