As for G'Mic testing...
My test image... 1080x902, 205kb png

Arrays and Frames...no problem.
Artistic...mixed bag. I had issue with slowness during preview and even slower when transferring from G'Mic to the workspace. A few worked quickly enough, I had most problem with..
1)
Ellipsionism ...this takes a long time to preview about a minute. Then about 5 minutes to transfer to the workspace. ( might just be my computer? ) Thinking now problem was with transparency? Anyway, I use a 512x512 png on this and not the above image as I could never get it to finish.
*mixed results really....each time either 5mins with one pic and 15-20min for another. Maybe is level of complexity. Who knows..upshot for me is it seems slow.
2)
Graphic Boost... Previewed quickly enough, took much longer to write to workspace.
3)
Pen Drawing... not sure of the result, didn't look very pen draw-y to me. Was more of a grey cast to the image. No error messages.
4) Water color... took long time to preview, then output didn't quite match the preview.
5)same with
Psychedelic Glassworks, output didn't match the preview.
6)
Pastell Art..hung up 2x (or at least seemed to me, ended up force quiting as I didn't feel like waiting for it)....this runs much slower than the previously mentioned Ellipsionism filter. I gave up on it.
ww