I generally follow the guidelines laid out in Vimeo's compression guide.
The US follows 24 FPS for film and animation, 29.976 FPS for video, and as high as possible for games. Europe generally follows 25 FPS for film. This just depends on how you want to animate; it doesn't really matter nowadays. However, if you animate in 24, export your video at 24. If you animate at 60, export at 60.
Video codecs are funny business, because not all available codecs are standardized, and not all distributors support all codecs. For example, H.265, or HEVC, is a great improvement over H.264, but is not widely supported. H.264 is one of the most universally supported codecs, so I would stick with that for now. Because of that, higher bitrate correlates with higher quality video; Vimeo's guideline for 1080p footage is 10k-20Mbps and I would err toward the middle if I want good quality. For 4k footage, I would use around 45Mbps.
This is subject to your... subject matter, of course. If you have a very still shot, higher bitrate will not make it look better. If you have lots of shaking camera, high movement, fast color change, film grain, etc, you will need a higher bitrate to maintain all that detail. A common effect of encoding with too low of a bitrate is smearing, streaking, blocking or ghosting of fast-moving objects. If you see some of these artifacts, raise your bitrate.
Your specific questions:
1 - Lossless compression does not throw away pixels of similar data. The decoder will decompress the data and it will look and behave exactly as the original footage. This will increase file size, but results in a decent reproduction of the footage, especially if you are compressing with H.264, which uses interpolation between I-frames.
2 - "Bitrate" is the target bitrate for the video. Sometimes it needs more to maintain fidelity, sometimes it requires less. Maximum puts a cap on the bitrate the encoder is allowed to use. Minimum is similar. You can safely ignore the minimum unless you really feel the need for a bigger file size. I would put a maximum of 5k-10k above your target, just in case the encoder needs the extra space. "Buffer" is like a pre-fetch for the decoder. How much of the video is pre-loaded to assist in playback and frame interpolation? I have never changed this setting in blender. You can safely ignore the buffer settings unless you're on extremely low-end hardware.
3 - GOP is described in Display Name's answer pretty well. It's basically the distance between keyframes (I-frames). More I-frames increases storage size, but it enables better interpolation.
4 - "Mux" is short for "multiplex," which is the combination of video and audio into one packet of data. I will refer you to the wiki page because muxing is somewhat large. I have also never used these settings in blender. Without audio, there is nothing to mux.