As for your question, maybe it is because Bandicam occupies much disk space and the game footage is in large size. If you want to capture game footage without lagging your PC, Apowersoft Free Online Screen Recorder is the best choice since I’ve used it to record gameplays without lags.
Here I’ll show you how to use it step by step:
Step1: You are able to record smooth game footage without changing default setup. But if you want to get clearer game footage, click Tools, tap Options, then choose Recordingcolumn to reset bitrate at 20000kps and frame rate at 60fps.

Step2: If you want to record game footage with commentary simultaneously, I suggest to choose Audio Input as System sound and microphone, thus you can add your voice into the game footage.

Step3: Open desired games, click Record, you can choose any mode (Full screen/Region/Around mouse) to meet your requirements. During recording, you can also edit the video with rectangles, circles, arrows, texts and many more.

After recording game footage in needed, it will be shown on its interface and saved in the default folder, then you can easily post the video on a website, a blog or on YouTube to share with people who have common interests.
Quick tip: If you get accustomed to using hotkeys, you can preset hotkeys in Options tab under Tools menu, it is easy for you to choose your favorite hotkeys.

All in all, Apowersoft Free Online Screen Recorder is simple to use, it supports to record game footage with outstanding quality, and the output game footage has no lag. If you still have no idea how to record game footage, please feel free to ask me on the comments page.