Before you design the POC environment, you need to gather some details and metrics from their existing physical workstations. You should have the specifications of the physical workstations (CPU, RAM, GPU, Storage), the resolution of the monitors and how many monitors are going to be used, a full list of all applications, and also some newly captured performance and utilisation metrics from these applications. That’s an absolute minimum. After you have those details, you can begin configuring the appropriate hardware specifications for the POC. At that point, you can also find out whether they are experiencing any performance limitations, you can then add performance where it’s needed into the POC specifications.
As you’ve already mentioned AutoCAD and Image Processing, your CPU choice should have a fast base clock (3.0GHz +). Forget about Turbo, you’ll have a better, more consistent experience with a fast base clock. Depending on the application requirements (how it scales it’s performance) and how many users you plan to have on each Server, you may want to use a pair of these:
A 12 Core variant of the 3.1GHz CPU is available. Also, there’s a 3.3GHz 12 Core variant as well. Which version you go for will depend on how the applications perform, but your minimum base clock should be 3.0GHz.
For the Image Processing, pay close attention to which components are used (whether it’s CPU (single threaded or multi threaded (if multi threaded, how many Cores can it make use of))) or does it use the GPU. If it uses the GPU, how much framebuffer and processing are used. If it’s heavy, you may want to look at an RTX 6000 / 8000 over a T4.
As a heads up, currently, the latest vGPU release (vGPU 10) doesn’t support the latest XenServer release (XenServer 8.1). So when you’re ready to build the POC, make sure you check the current supported versions and if needed install XenServer 8.0. That will allow you to run XenDesktop 1912, Windows 10 1909, and vGPU 10. You can then simply upgrade XenServer to 8.1 once it’s supported.