We spent 2 weeks last time and have been there for 1 week stays several times across the years and still haven't seen all of it. Stay at Fishing Bridge if you want FHU. It's an ugly parking lot but it's all there is. And we were only there starting in the late afternoon/evening.
Remember that park is bigger than some small eastern states, there is a lot to see and many trails to walk. 4 days at the Tetons isn't too long if you get out and do trails, swim in the lake and see things. Ride the ferry across the lake and go on Ranger walks.
As mentioned there are many threads about YNP here it is a very popular question. Oh yeah the downside is the traffic. People stop and block the roads which have a 30-40 mph speed limit anyway, whenever they see a chipmunk or something larger. Which they will. The nps will also have at least one long section of some road torn up for rebuilding. So be patient.