Premiere Pro and After Affect

PPro is also very useful to AE. It's best to use PPro for final audio spotting and other audio works (or once in PPro, send the audio to Adobe Audition, if required). PPro is also ideal for checking your AE renders since PPro will playback a single video track in realtime and also for output to MP4. And if you spot an AE issue in PPro, you can go back to AE and render just the part(s) that require a re-render and this of course speeds up workflows.   

Premiere Pro is a professional non-linear editing app with powerful tools, and it is powerful enough to edit a major feature film. Many have been cut on Premiere Pro. Audition is a dynamically linked audio mastering app that can be used with Premiere Pro to produce professional-quality audio production in Premiere Pro if the built-in tools are not up to the task.

After Effects is NOT a video editing app or NLE. It is a motion graphics, compositing (Visual Effects), and animation app specifically designed to do things and create shots that cannot be created in an NLE like Premiere Pro. Most professionals limit their After Effects compositions to one shot. Mine are usually under 7 seconds because most of the shots in the movies I edit are less than 7 seconds. The only time you would want to make a composition longer than a few seconds or include more than one shot is when you must transitiion between shots in a way you cannot do in your NLE (Premiere Pro). For simple effects you can use Dynamic Link to directly edit a shot or a short sequence in Premiere Pro using After Effects. For more complex effects and animations it is better to just bring the shot into After Effects using copy and paste, then complete the work and export a production format digital master that you can drop in the sequence in Premiere Pro. Most of my FVX shots are very complex, some have more than 100 layers and effeects so almost all of my AE comps are rendered and then added to the sequence timeline in Premiere Pro for final edit.

I hope this helps. I'll give you one more suggestion. If you are going to render your After Effects compositions do not use MP4, h.264 or even h.265 because these are interframe compressed, color compressed and lossy formats. You want to use a frame based visually lossless format like ProRez, DNxHR, or even an image sequence to render your comps for editing.

Let us know if you have any other questions.

There are many VFX and graphics tasks that are better to do in After Effects, if not exclusive to that program. Rotoscoping, compositing, masking, keying, animation, motion tracking, 3D camera movies -- it's a very robust program and a good complement to Premiere.