I stream with my Mcwill modded Lynx on stream so might be able to help here.
The output resolution on direct VGA would be 640 by 480 with the game in a smaller display area within that size. If you connect to a standard VGA monitor than it should be accurate aspect ratio but just in a smaller display size.
You can use a decent VGA to HDMI box to get it the signal out to a tv or capture card but the quality varies wildly in terms of noise so may a bit more for something decent and make sure you buy the right direction as its a one way signal.
You will need one of these converts to connect to a Frameister so again the best quality you can send it will help. Once there I find the image a bit soft so add sharpness to +1 but in general it seems good and of course you can use the zoom feature to fill out your display. There is no color profile that I am aware of but I would recommend to add some saturation.
I am going to test with an OSSC soon to see if it looks any better but here is some video so you can get an idea of what it might look like:
in this stream I am going from Lynx--> VGA to HDMI converter-->Frameister--> El Gato HD60 Pro PCI capture
let me know if you have any other questions!