Generally anything that improves OS X Metal performance will improve graphics processing in Capture. Depending upon Mac model/age, CPU, RAM, eGPU, and GPU card, the Mac Mini and Macbook benefit from using an eGPU. If you haven't seen it, there is a website:
https://barefeats.com/index.html
that provides a lot of testing data of eGPUs and graphics cards in various Apple computers.