If this is a master, and there is another hall bath for kids, I would only keep the tub if there is room for a good sized shower, double vanity, toilet AND separate soaking tub, which it does not appear there is.  

I am considering a property listed at $800,000, which includes a 2-bedroom, 2-bathroom main house (1100 sq/ft) and a separate ADU of the same size.

Your problem with that property is neighborhood, not size--- that's right around the corner from Joy Park Homes.

Probably go flat on larger living area walls.It's always American Craftsman for us when I can get the right size.

Assuming that the units are the exact size, you taxable gain would be allocated 50/50 between the owner occupied unit and the rental unit. 

The sample size is too small.

Given the price point and size, your units may appeal to young professionals, students, or single individuals.Online Presence: Utilize online rental platforms extensively.

I am married and my family size is three (me, my wife, and 3 yrs daughter).

A mini-split will meet that requirement (as long as it's sized appropriately) whereas a window unit will not.

As a broker you might be motivated to inflate the price of the property, after all your commission depends on the size of the transaction, and with fiduciary duty to seller you will try to get top dollar for distressed home in dire need of rehab.