Spillover can be very significant, regardless of training. It depends on the makeup of the trainee. The body doesn't work like that (first muscle, than fat) for most people. It's a constant flux in and out of the cells and the overall trend over weeks and months matters for your body composition. For that reason muscle gain (as a more advanced trainee) tends to require some with fat gain if you want progress at any decent speed (Leangainers often don't). Why wait for a couple hours btw? There is no magical switch flipped, which prevents fat gain after waiting a bit longer. You probably misunderstood how important some of the processes after a high intensity training session will be for body composition. Read the article above for an explanation.
Depends on caloric density. I have no problem overeating vastly on good ice cream or nuts& dried berries. Easy to get down an additional 3000kcal.