No problem. I’m happy to help.
There is a huge potential for customization, yes. As you already recognized, the MainUI uses mostly F7 components which allows to create a lot of fancy stuff. (for example: Keypad widget, Sonos widget, Multiroom Audio Player widget, Aircon controller, Camera widget, Weather widget to only name some of them - you can find most of them in the UI category of this forum)
Assuming that you’ve already read the documentation threads (1, 2 and 3) a usefull next step would be digging into the f7-documentation itself, which you can find here and here - on a detailed component level.
It would also be usefull to look into the above mentioned widgets and try to understand what was done there and maybe adapting them to your liking to get comfortable with the YAML-syntax of the widgets.
Last but not least, It helps keeping an eye on the openhab-webui github repo and try to keep yourself updated with the latest changes and the examples that comes with the commits. @ysc for example is doing a great job providing examples to nearly everything he implements into the MainUI.
Hope this helps a bit.
P.S. Here you can find the standard widget-components (in raw vue-markup) that are currently implemented into the UI. This might also help to see what components were used.