Low framerate (not lag) in preview

Changing the comp frame rate to 120 fps is not recommended at all. Check your Preview panel. The Frame rate should always be set to Auto. 

The frame rate of the composition has nothing at all with how long it takes to playback a video. If a composition is 10 seconds long, changing the frame rate from 10 fps to 120 fps doesn't change the speed of the playback. The comp still is 10 seconds long. Changing the frame rate in the preview panel does change the time it takes to playback a comp. If your 10-second comp is 25 fps but the preview panel is set to 12 it will take 20-seconds to playback the comp. It's just like changing the frame rate of the projector. If you want longer previews set your Preview Panel to Skip 1 or even 2 frames because all you should be checking when you ram preview is the staging (framing) and timing. Your preview panel should look like this. The frame rate is enclosed in parentheses and that means it is set to Auto.

The ability to ram preview depends entirely on allocated system resources, comp settings, and preview resolution. When you are working on lyric videos (dynamic text animations) you should have the Comp panel resolution set to Auto, the Magnification Factor set to 50% or less, all effects off,  motion blur off, and probably Fast Previews set to Fast Draft. All you are looking for when you are "editing" is timing, framing, and staging of the animation. Just like traditional animators do, you start with a low-resolution Pencil Test. When the scene works, not when the whole edit works, you turn on all of the effects, turn on motion blur and check a couple of hero frames for what I call Ink and Paint, then you render that section and move on to the next scene. A scene in a lyric video is a comp, and your scenes should not be longer than a sentence or two or a few bars of music. Create your scenes and then Edit the scenes in Premiere Pro. That's how you work efficiently. 

I recently posted a screenshot showing how I produce explainer videos, which are a lot like Lyric Videos. The most important part of this kind of workflow is setting audio markers in the audio track and dividing the scenes up into comps. Maybe it will help. Trying to edit a complete Lyric Video for a three or four-minute song in one comp is a bit nuts and it's going to take you a lot longer to finish the project than it would if you add markers to your audio track and break the song up into scenes or phrases.

What is the "improve perfoprmance page"?