You might be thinking of Fractal Explorer it sort of does that. Apo though, it has the small Adjustment window for setting thing up, adjusting Gradient etc. but the main window is where you see the large representation of the fractal but that window is Not the Final render just a larger representation of what the Final will be like. The Quality of the small adjustment window can be changed by right clicking in the window and selecting Low,Mid, High quality and those settings are setup in the Options on the Displat Tab.

Any adjustment to the position, Gradient, zoom or whatever in the small adjustment window will trigger a render in the main window, it's quality is controlled by the Quality set in the Rendering Quality box on the Toolbar from 15% to 1000%, I usually use 50% for getting things set and then when I'm happy run one at 1000% to see if the full quality will be what I want, then go to the Final Render and let it go. I set the Main window at 1000x 500 for setup and do the Final Render at normally 2500x1250, usually takes from 1 to 2 hours to render depending on the complexity of the Frac, plus I have an old slow Puter.

Remember...No matter where you go there you are