Set your zoom factor to 50% for most work and set resolution to auto. It just takes time to render the changes. Also, make sure your version of AE is up to date. The trick to working quickly in AE or any compositing and motion graphics app is to get the position and movement down before you add any effects to your elements. I call this a pencil test because it's the same idea that traditional cell animators use to get the cartoon working and the action right before they send the pencil tests out for ink and color. If you have already added a bunch of effects you can turn them off in the timeline and fine tune the animation. When you get the motion right and everything looks good set the Scale Factor for the comp at 100%, pick a few critical frames and turn on motion blur and effects to see how things look. If you really must do a ram preview of parts of the shot that are critical, then send the comp to the render cue.
Here's another hint. Keep your comps short. If you have 20 shots that are cut together that you need to add UI elements to then make 20 comps and keep things simple. Then you can render the shots and edit them together in Premiere Pro. While this doesn't sound as efficient it actually is a far better way to work and will save you a bunch of time in the long run. AE is great for shots or short sequences. It's horrible for editing.