DR 17 Free: Select GPU?

I have a late-2019 iMac coming. With regard to FREE DR 17:

I intend to install a high-powered external GPU to overcome the paltry on-board chip, and want Resolve to ignore the internal and talk to external only.

Can you choose which GPU you want Resolve to use in the free version, or is that a Studio-only function? (I know Studio can use multiple GPU's, this isn't that situation.)

?? Nada??

There is a selection box in the settings.

However on PC (windows/linux) when multiple internal GPU you really want the display to be plugged in the GPU being used because OpenGL/OpenCL interop only really works that way and drivers from different vendors don't necessarily cooperate well.

I have no idea how OSX deals with eGPU and with an imac where you obviously can't connect the screen to the egpu. Some people use eGPU with OSX laptops AFAIU so maybe it works ... but then it might also depends on which GPU exactly ... YMMV.

In short : Yeah there is a selection box ... whether it will do you any good or not ... TBD.

The free version of DR doesn't much make sense on a modern iMac. You internal GPU will be used for the GUI monitor and AFAIK you can't use the eGPU for processing only. Shuffling every frame to be the displayed back and forth will only slow down your eGPU.
But if you get Studio, your eGPU will support complex effects (like temporal NR) nicely.