ADU Questions

I have an ADU apartment in a detached garage. I have one mortgage that covers the entire property (home + garage/ADU) and the city issues one property tax statement. It was rented all of 2020.

What are the different tax ramifications if the ADU is considered a rented space in a single family home vs a multi family duplex?  

Another complication, I had to refinance the mortgage in 2020 to drop my ex husband from the mortgage & title.  I need advice on how to enter in the information for the mortgage, refinance, insurance, property taxes and expenses. It seem like there are different strategies if the ADU is rented space in the family home vs multifamily duplex.