The verdict

Local AI
Nvidia RTX 5090 has more VRAM (32GB vs 24GB) - up to ~33B (Q4).
Fit
Nvidia RTX PRO 4000 Blackwell SFF is easier to add to a mini-PC (low-profile PCIe).

Which wins for each job

Job Nvidia RTX 5090 Nvidia RTX PRO 4000 Blackwell SFF
Plex transcode ~12 streams ~12 streams
Frigate NVR ~25 cameras ~25 cameras
Local LLM 32GB VRAM win 24GB VRAM
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 Nvidia RTX 5090 Nvidia RTX PRO 4000 Blackwell SFF
Price (list) $1,999 $1,500
Type gpu gpu
Interface pcie pcie
Transcode H.264/HEVC/AV1 (NVENC Blackwell 4:2:2) H.264/HEVC/AV1 (NVENC Blackwell 4:2:2)
Frigate detector TensorRT TensorRT
TOPS - -
VRAM (GB) 32 24
Low profile no yes
GPU sharing - vgpu
Power (W) 575 70