An awesome recommendation of a screen recorder.
I would have recommended it, and I use this as well. There are countless of features, seriously. Give it a download so you can see for yourself. Please take my word for it: paying for the full version is well worth it! Believe me!
In my experience, yes my game did lag because the app is currently set to save recorded videos to my internal storage, and thus if it takes a while recording, the file size will get larger and more disk space are required. It is better to move previously recorded videos to external storage to free up space. (android user here)
But if you are an ios user, i think you should have a larger memory disk space for that. :)