What is the right way to export videos with different FPS? I know about rendering and exporting. But it's about some video clips having different FPS. For example, my current practice project has: 

1. Motion Title (29.97 FPS) 

2. Video clip 23.976 FPS 

3. Other video clips with 24/23.976 FPS.

I have edited all of them in After Effects. And I'm going to export them as .mov/.avi (lossless) and finally export as compressed format (.MP4) using Premiere Pro.

For this, I'm supposed to change Pr sequence settings to 29.97 FPS and drag all clips into it.

Now question is: Would it affect the quality of the clips that don't match with 29.96 FPS?

Another question: Is it better to compress them individually with their respective FPS settings and COMBINE them later with some software (If such professional software exists)?
Generally, all of your assets should be converted to the same frame rate as your final output frame rate before you begin editing. If you do not convert them beforehand, you may have issues with timings. Things that are supposed to be one length end up being a different length. This is especially true if you export a variable frame rate file. Suddenly a 30 second file becomes 28 seconds, or 33 seconds, or some other length. The audio and the video end at different times. Things may play right in some places, but they may be wrong if they are processed and played elsewhere.

To summarize:


Convert all assets to the final frame rate before editing.
Set your project to the correct final frame rate.
Do not export a mixed or variable frame rate file.