Hmmm
When I looked at various ZWO cameras for solar imaging - ASI 183 etc I found the frames rates when using a ROI very fast!!!
I'm in the process of changing over from the ASI183 (technical issues when using narrowband solar) to an ASI 1600 and anticipate being able to achieve high frames rates on the spectroheliograph.
(I can get >400 fps with the ASI 174 when applying ROI. I use FireCapture)
https://astronomy-imaging-camera.com/product/asi1600mm