I'm going to assume your a gamer? If your working with 60fps footage or anything above 30fps that's a huge problem. Camtasia's timeline only supports 30fps footage.You can place 60fps footage on it but it's reduced to 30, playback without animations can be sketchy. Add effects and it's all over. If you are using Camtasia for gaming, you want to working with 30fps footage.
Unfortunately,even with 30 fps footage. There's no getting around lagging and freeze altogether. Especially with HD/4K content and Camtasia's inability to pre-render timeline content.
As animations become more complex, the lagging becomes more of a problem.