Note9: Can you sync DIFFERENT calendars on google calendar and samsung calendar at the same time? I have personal and business calendars from completely different accounts and I don't want them to show on both apps.

When I select specific calendars for Google calendar for Android, I can't prevent Samsung Calendar from showing the exact same changes and vice versa.

Can you select only Calendar A from Account A on one calendar app and only Calendar B from Account B on another on Android?
Candl Apps makes two calendar widgets - one called Calendar Widget: Month and another called Calendar Widget: Agenda. 

You can add calendars to these widgets which will not automatically change the visible calendars on other calendar apps.

Here are the links to the play store:

Month
https://play.google.com/store/apps/details?id=com.candl.chronos

Agenda
https://play.google.com/store/apps/details?id=com.candl.auge