We love going to Universal and have rented several vacation homes in the Kissimmee area. I would suggest looking for a home off of Poinciana Blvd, which is south of 192, and east of I-4. This road has decent access to I-4, and there are good shopping/restaurant options on 192, without the Disney traffic found west of 192. If you can find one closer to 192 than further away, that is even better. We are staying at the Terra Verde resort for our next trip.
From all my research, it seems difficult/impossible to find any vacation homes closer to Universal/Sea World. I think there must be some kind of zoning restrictions further north of Kissimmee? There are some 2-3 bedroom condo type rentals closer, but no private homes that I could find.