Not much that I've planned out in advance, but I did come up with some general ideas for how the two races interact.
Before the war, things were pretty much open between the two groups. Monsterfolk and humankind would often go into each others' lands to trade goods, though it was usually for only a short time and few ever decided to stay permanently. There were a few small towns near the border that were founded by both monsters and men, though they often had very small populations as few monsters liked living with that many humankind, and humankind felt the same way about the monsters. Battles between the two happened, but they were usually small in scale and relatively rare; no more intense than the small wars between different animal tribes, or between the humankind's kingdoms.
After the wars however, there's been significantly more animosity between the two. While humankind visiting monster lands were rarely turned away and generally trusted, now they're always viewed with suspicion, often with the monsters asking them to surrender any weapons they have. Trade happens, but is very rare. However, the monsters usually don't openly attack humankind unless they're attacked first. The kingdoms, on the other hand, are much worse. Many of the monstergirls that lived in areas that were attacked were captured and turned into slaves, something that was almost unheard of before the wars. Now it's not at all uncommon to walk down a street and see many of the people walking along with a monstergirl slave in tow. After the wars ended, most cities enacted laws making it illegal to attack or try to capture a free monstergirl, but far too often the patrolling guards would turn their backs when a group of humans attacked a monstergirl, or even tried to arrest the girl if she managed to fend off her attackers. Monsterfolk convicted of any sort of crime in human lands are given a short, often unfair trial and sold into slavery, no matter how minor the offense.
As for basing it off of MGQ, I actually haven't played it. (Not a fan of F/m sex scenes, though I would instantly buy it if the main character were female.) I may go to the monstergirl encyclopedia images for ideas for how the different tribes are, but I may also come up with my own ideas for things.