Welcome to the thread, @CAC-ALD. 

I'm here to answer your queries in handling your file when working at home and office.

As for your first question, you were right that you should be backing up locally. Then, move the backup file to the OneDrive if working at the office and vice versa when working at home since only one computer can access the data file(s) at one time. By doing this, you'll have the most current updated file.

To know more about accessing your QuickBooks Desktop (QBDT) file stored at a different location, check this article and go to Option 3: Set up or open a company file from a remote computer section: How to set up QuickBooks Desktop to work from home.

Then, for your 2nd question, to ensure you won't miss any data when doing a backup, you'll need to move the entire file every day.

For additional reference, here's an article to further guide you in managing your company data and your business's growth using QBDT: QuickBooks Help Articles. It includes topics about data security, banking, and expenses, to name a few. You can click the + More topics button to view other selections.

Fill me in if you need a hand when running your business in QuickBooks. I'll be here to make sure you're taken care of. Keep safe and healthy.