Is there a simple way to determine how to set the q up on your cleats correctly? If I eyeball my pedal stroke is there a way to determine by foot position etc whether I need to go wider or narrower?

I go by how my knees feel. If I have the cleats not set up right, I usually get knee pain after a short (30 minutes or so) ride.

For me, the more critical thing is the angle of the cleats. I found that using the wider float Look Keo cleats (red) is much more forgiving.

I concur. Maybe there is some threshold where Q factor becomes important, but within the range of most road bikes, doubles and triples, I never noticed a difference I couldn't get used to. I just set the cleats so my feet are pointing comfortably straight ahead and everything (barely) clears the cranks and chainstays. Make sure to allow for winter booties.

In Andy Pruitts book he put this question in the "what we dont know but wish we did" section. It makes a huge difference for me and each foot is different. Trial and error and feel have been my guide.
The "correct"Q is also closely linked with the amount of arch support and varus/valgus wedge you use. Also adjusting Q will likely change the required angle on your cleat. I have messed about with this extensively and it can make a huge huge difference to foot and knee comfort

RAD kit

https://bikefitkit.com/fit_kit/rad_kit.php

Probably overkill, particularly if your pedals ave a lot of float. But if you have knee issues might be worthwhile.