Capture One relies on both CPU and GPU for processing tasks.
Capture One information about OpenCL: KB 1720

How to find the OpenCL benchmark index:

Open (Windows): C:Users[USER]AppDataLocalCaptureOneLogsImgCore.log
Look for the latest line similar to:
2018-03-24 08:32:30.939> OpenCL benchMark : 0.075741
0.075741 is the index of your GPU

OpenCL vs CUDA / OpenGL

The technology used is OpenCL (not to be mistaken for OpenGL/CUDA),
THIS is an interesting article about the differences.

GPU comparison

To give you an idea of what the performance value of a GPU is I’ve gathered benchmark results and put them in the table presented on this page.
You’ll see “gaming cards” perform very well, the “pro cards” are less capable if you compare “result per buck”.

The GPU names link to entries on TechPowerUp’s GPU database.

If you want to compare GPU’s to get an idea of the difference you can use GPUBoss for instance.
For instance, you’ll find a comparison of Nvidia GTX1070 vs AMD R9 290X on this page.

10.0413363Windows PCNVIDIA GeForce RTX 2070Intel Core 4790kMicrosoft Windows 10 (x64)11.0
20.0536725Windows PCNVIDIA GeForce GTX 1080 Ti23.21.13.8871Intel Core i7 8700 3.70GHzMicrosoft Windows 10 (x64 1709)11.0
30.06948010Windows PCNVIDIA GeForce GTX 1080 FTW (EVGA)Intel Core i7 7820XMicrosoft Windows 10 (x64 1709)11.0.1
40.07403711Windows PCAMD Radeon R9 290X17.12.2Intel Core i7 6700K @ 4.60GHz (OC)Microsoft Windows 10 (x64 1709)11.0.1
60.08544414Windows PCAMD Radeon R9 280X17.12.1Intel Core i7 4790kMicrosoft Windows 1011.0
70.08478413Windows PCNVIDIA GeForce GTX 1070388.13Intel Core i7 3770Microsoft Windows 10 (x64 1703)10.2
80.08583215Windows PCNVIDIA Quadro P5000 (ECC on)390.77Intel Core i7 7820XMicrosoft Windows 10 (x64 1709)11.0.1
90.09624016Windows PCAMD Radeon RX 580 Nitro+ 8G (Sapphire)Intel Core i7 7820XMicrosoft Windows 1011.0
100.10604217Apple Mac Pro (2009)AMD Radeon HD 7950 Mac Edition (Sapphire)Intel Xeon W3520 @ 2.66GHzMac OS X10.2.1
110.12328818Windows PCNVIDIA GeForce GTX 1060 3GB398.82Intel Core i7 2600K CPU (OC)Microsoft Windows 10 (x64 1803)11.2