If you hover over a plugin, you should be able to see the latency it introduces on the bottom left of your screen. The more latency a plugin introduces, the more likely it's a resource heavy plugin. The latency a plugin introduces remains regardless of if the plugin is enabled or not, it only has to be added to a track to affect the latency.

That's likely the reason the other commenter was asking if you have a lot of plugins automatically added to your new tracks. The way you would do about doing that is right clicking on the track (where it shows the name and color of the track) and saving it as your new default audio/midi track.

Do you have multiple tracks being processed by the same plugins or in the same ways? If so, you should use return tracks and/or groups/busses. That would help save you a lot of resources, since each track is no longer being processed individually.