Got it, thanks!
1. The distance unit depends on the language chosen in the settings. Since the traditional measure unit in the USA is miles, it will be used when choosing English (US). However, if you choose, for example, English (Australia), miles will be replaced with kilometers:
2. We already have a request for the Marker size setting, and you can upvote this idea here - Setting to change marker size
3. Map Center and Zoom options, where you can set auto or custom values are already available on the Settings tab.
Do these options work for you or you wanted to have Min/Max Zoom and Map Bound restrictions as well?