Notice there are disabled words in the Settings menu that define separate sections: Project, Player, and User Interface.
I find it useful to change those settings to lower res/FPS for the sake of reducing lag in the preview while editing.
That is a bad idea. See the docs:
I don’t see the purpose in having those settings affect the exported video.
You have it backwards: they primarily define what is to be exported. You need to define your project attributes ahead of time. Settings > Preview Scaling, on the other hand, is a way to preview things at a lower resolution. There is nothing like that for frame rate though.
The export settings are the ones that are redundant. They let you resample a project from old attributes to new ones - not magically but through simple frame rate adjustment (i.e. dropping or repeating) and scaling. They are best used for down-sampling from high to low. Why? For special situations where you need to output a project to a different target. If you do not like that, then do not use them and always use Video Mode. I did try to guide you by putting these into the Advanced section of Export and by putting Video mode into the New Project view of the startup screen.
Some people want me to dumb it down more so it is harder to cut yourself. Other people want something more complicated and fully featured.