Exporting the best quality video

In general you should keep the settings from your original recording device. If you recorded in 60 fps – keep it that way. If you recorded in 30 fps – it doesn’t make any sense going to 60fps – unless you want unnecessary big file sizes For export you can use any format you like but for sake of interchangeability and flexibility i would opt for mp4 h.264 or h.265 codec with reasonable quality setting (default is 55% quality – which is sufficient for general purpose) You can go up to 60 – 65% quality – leading to bigger file size and little better visual quality. Avoid quality settings above 70% – you won’t get any better with visual recognizable artefacts e.g. – just creating huge files. There are also completely lossless formats for intermediate operation – if you want to finalize your work later on and work in intermediate steps so to say. But this is not recommended for permanent storage just to view it on some media – as it just wastes space and is complex to decode (needs high cpu-power for viewing).
Do a little search here – there are lots of topics dealing with video quality and codecs

Its not so much a matter of B-frames and GOP, just keep the standard settings. Bigger GOP leads to little smaller filesize and doesn’t affect video quality much. Its best (imho) to keep GOP between 15 (prefered by Youtube) and 60. The bigger the GOP the more complex it becomes to edit the results afterwards as you have 60 frames in one compression group. This is more a matter of the codec you use and the compression algorithm – don’t bother too much about that