Obs should not lag your game. Chances are, you are using the default settings of OBS when you first downloaded it and THAT is what causes the lag. If you haven't changed anything, the default encoder is set to x264 and you have your rate control to CBR. I know that everyone's computer is different but if you have a graphics card, you should be able to change the x264 preset to NVIDIA NVENC which utilizes your gpu and takes the load off the cpu. I am not a "tech" expert but the Java version of minecraft hogs the cpu so much that running obs in the background will cause problems to both the recording and your game experience because you are overloading your cpu. Try other rate control as well- Change your CBR to CQP. In the end, a player shouldn't feel that they are pressured to take recordings of their game to report hackers. That's the staff's job. If you feel that there are too many hackers when you play, trying playing at a different time. Better yet, find a buddy who is good at the game and try to 2v1 any hackers by being in a party.