The verdict

Plex
Nvidia RTX A6000 transcodes more streams (~24 vs ~12).
Local AI
Nvidia RTX A6000 has more VRAM (48GB vs 24GB) - up to ~33B (Q4).

Which wins for each job

Job Nvidia RTX 3090 Nvidia RTX A6000
Plex transcode ~12 streams ~24 streams win
Frigate NVR ~25 cameras ~25 cameras
Local LLM 24GB VRAM 48GB VRAM win
Fits a mini-PC full-size PCIe, DIY build full-size PCIe, DIY build

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 Nvidia RTX 3090 Nvidia RTX A6000
Price (list) $800 $4,000
Type gpu gpu
Interface pcie pcie
Transcode H.264/HEVC (NVENC Ampere) H.264/HEVC (NVENC Ampere)
Frigate detector TensorRT TensorRT
TOPS - -
VRAM (GB) 24 48
Low profile no no
GPU sharing - vgpu
Power (W) 350 300