I'm using the Telsa P4 for Plex transcoding. I fired up 8x 4K HDR ==> 1080p 8mbps (with HDR tone mapping). This GPU handled with lots of room to spare.
I bought a 3D printed fan shroud to blow air onto the GPU and keep it cool. Search here on ebay and you'll find them at reasonable prices. The GPU temp was 37C.
From some back-of-the-envelope math, I'd estimate that this has enough GPU memory to handle ~20 transcodes. Your mileage may vary.
OS: Ubuntu LXC running on Proxmox (Debian).
Still early days, but the product is recognised as advertised, looks to be brand new and works like it is supposed to. I have attached my own 3d-printed fan shroud and it stays nice and frosty (40-45C idle) in my home server, transcoding every now and then. Can recommend!