OK - if the video looks 'pixilated' and blocky, you may be running old camera firmware. Initial versions of the camera software had a bug that meant 120fps video was incorrectly encoded. Check which version of the firmware you're running and update as necessary.
Secondly, you need to understand that the CGO3+ records variable bit rate files. So unlike some cameras, the bitrate goes up and down according to how much action the camera is encoding. Big visual changes from one frame to the next will result in higher bit rates, and low changes result in low bit rates. This changes constantly during your video.
The CGO3+ has a maximum bitrate of 60Mbs - that means it will increase the bitrate up to that amount but no higher when encoding video. In practise, the most I've seen is about 55Mbs, but it's rare to see it that high. This does not mean you're getting 'lower quality' video, just that it didn't need to use more data to encode the frames. You can have 10Mbs video and it can still be pixel perfect. It also means that you can't "set a bitrate" for the camera. You ask it to record and it does the maths in the background. The limit is good enough given the bit depth (dynamic and colour range) of the camera.
When it comes to cards, make sure you're not using clone cards (I know a few people who've been bitten by this), and copy your files to your PC (ideally onto an SSD) before editing - playing back from SD is fairly unreliable even on high end rigs. The CGO3+ video is tuned for efficient writing rather than playback, so if you're using a decent video editor, get it to transcode ('proxy files') before editing to get smooth playback.
