How much customization can be done on Service Calendar?

Hi everyone!

This is more general question. I would like to know the amount of customization work that can be done on Service Calendar.

For example:

Can we change the default view?

Can we change the default zoom level? For example every 15 minutes instead of an hour

Can we color the Users based on a field? Not the appointment type but the users.

Can we filter the calendar using javascript based on a date?

Thanks!