2017 34" HP ENVY Curved All-in-One (RX460) [7th,4C,T] + RX 580 @ 16Gbps-TB3 (HP OMEN Accelerator) + Win10  

System specs

34" HP ENVY Curved All-in-One - 34-b010d, i7-7700T, 16GB Ram, Intel HD Graphics 630, Rx 460, Win10

eGPU hardware

HP Omen Accelerator, Rx 580, official Apple TB3 cable 

Hardware pictures 

Installation steps 

Pretty straight forward, just follow the official instructions here:

https://support.hp.com/sg-en/document/c05573720

Before you begin

For best results while installing and for complete feature availability, follow these instructions:

• Install the OMEN Accelerator app only when the hardware box is plugged in and has been detected by the host computer. Like any other device connected via Thunderbolt, it might take several seconds for the host PC to detect the hardware.
• Install the OMEN Accelerator hardware after all the hardware drivers have been installed and the BIOS updated. Reboot the computer according to the driver installation requirements.

Follow these important steps before connecting the OMEN Accelerator to your computer:

1. Install a graphics card in the OMEN Accelerator, if one is not already installed. For instructions see, Installing a graphics card.
2. Update to the latest BIOS version for your computer:
   HP Notebook PCs - Updating the BIOS
   HP Desktop PCs - Updating the BIOS
3. Install the Intel Thunderbolt Firmware package (SP80611) only on the following HP products being used as a host PC:
   • HP Spectre Notebook PC13-v0xx series
   • HP Spectre x360 Convertible PC13-w0xx series
   • HP Spectre x360 Convertible PC 15-bl0xx
   • HP ENVY All-in-One PC 27-bxxx
   • HP ENVY Curved All-in-One PC 34-bxxx
   If your computer is not an HP product, contact the computer manufacturer for information about Thunderbolt firmware.
4. Install the latest Intel Thunderbolt Controller Driver on your computer: SP80671
5. Connect the power cord, and then connect the OMEN Accelerator to the Thunderbolt 3 port on your computer.
6. Download and install the OMEN Accelerator - Realtek LAN driver: SP80673
7. Download and install the latest graphics driver from the manufacturer's website:
   • NVIDIA
   • AMD
8. Install the OMEN Accelerator app: SP82396
9. Install the OMEN GA1-10 Accelerator firmware update: SP86866

The rest of the instruction on actually how to add a card or anything else is listed on their support page.

Benchmarks 

Valley

Rx460 iGPU

Rx580 eGPU 

3dmark

Rx460 iGPU

Rx580 eGPU 

Aida64

System

This machine is an AIO, but it does have an HDMI in port. So technically you can run it as an external screen too.

Everything has been tested on the internal display. If you run a cable from the eGPU to the the HDMI-in port and then switch over to it, it squashes the entire image and messes up teh aspect ratio. I am not entirely sure why, but that's what it does and you can't change it. I also ran the numbers while in squished mode, and they were the same. 

Comments 

The only issue is that you're limited to 2x PCIex as pointed out by @joevt, but I'm happy with the outcome so far.

I will be testing a RTX 2060 down the line.