velocity differs

I am a self taught newbie working on a traditional character driven horror series. I am having problems with the playback speed of the scenes between my project and the preview movie option. While in TBS some scenes playback too slow, while after rendering a preview, the playback is super fast… I realize some scenes may be too heavy, but is this the reason? My first episode is finished drawing, and now I need to add the soundtrack, but the playback is way too fast, If I add the sounds, will my characters sound like chipmunks?
I’m working on a brand new Mac purchased in November and as I said I am self taught, so It may just be me… ???

Two comments:
(1) In animation it is always best to animate to the sound track and in computer animation that usually means put the sound track in your project first thing. Specifically in TBS you import the sound at a fixed FPS and don’t change that FPS later or your sound sync will get messed up. Typically 24 FPS is a good choice, some people like 30 FPS as well.

(2) As a general rule rendered playback is the only way to accurately see what you will get. Internal playback is not reliable in that regard.

Keep at it -JK

thanks for your help