Keyboard Navigation
The problem with keyboard navigation is, Floating Menus usually never get keyboard focus so they don't interfere with the actually active application (unless a textfield or something like it is clicked inside of them). However this is definitely planned and there are a few options (if you can think about any other please let me know):
• Allow keyboard navigation while the mouse hovers the menu
• Allow keyboard navigation once activated via some trigger
• Have an option to gain keyboard focus when showing the menu via an action
• Catch all arrow keys while a floating menu is visible and use them to navigate. If multiple menus are open, it would need some priority setting.
Maybe this can be continued here: Keyboard navigation for floating menus - #6 by little-big-h
Overshooting buttons:
•This should be doable, I'll have a look 
Formatting Options:
• I think I don't want to offer a full text formatting alternative for hover, but I can offer a hover color that then applies to the entire text
• Hover color for SFSymbols will be added with the next version