The smoothness of play back is depending ontghe hardware in your computer.
Usually your proccessor speed, available Ram storage, and graphics card. for a smoother play back prerender your footage. hit the zero key on the number pad to see and difference.
For this type this in youtube search bar. How To PreRender with Audio in After Effects and also this AE Basics 62: Export 8 - Understanding Pre-render creativecowofficial is the best channel to go to to learn anything you need to know. Also the help menu in your program is the best way to learn as well even though its time consuming and a boring read.