Alex, from what I have been able to find out the HEQ5 pro and the NEQ6 both have the same stepper motors and some of the increased payload capacity would be due to the heavier tripod supplied with the NEQ6. I have the HEQ5 pro (mounted on a pier) and it seems to easily push a 10"f5 newt, anything lighter easy as.
Here's a comparison link
https://astrobackyard.com/heq5-vs-neq6/