Calculate the room's need
Ask for the room's heating and cooling loads using its actual windows, insulation, exposure, and intended temperature. Include whether the door will be closed.
The useful comparison includes mild days as well as winter and summer extremes. NEEP emphasizes minimum output as well as maximum capacity when selecting heat pumps. NEEP sizing guidance.
Ask the designer to show the relevant performance data for the exact indoor and outdoor combination. The smallest head's label alone may not describe what the complete system can deliver to that room.
Consider arrangements that fit the rooms
Request options for serving several small rooms through an appropriate compact ducted design, a different approved equipment combination, or a supplemental plan using existing heat. Have qualified providers scope related building or duct work.
Each option needs to explain closed-door coverage, control location, sound, access for care, and any necessary construction.
Do not accept a plan that assumes bedroom doors stay open unless that matches how your household lives.
Ask about low-demand operation
Have the provider explain what the proposed system does when the room needs very little heating or cooling. Ask how that affects temperature swings, cycling, and summer moisture control in this particular design.
Those are questions for model-specific performance and design evidence, not a reason to assume every small head will cause a problem.
If equipment is already installed, record actual temperatures, settings, run and stop patterns, and measured humidity if dampness is a concern. Keep installer settings unchanged while the provider checks the design and controls.
Your next step is to request a room-load and minimum-output comparison for each option. We would choose the arrangement with a credible plan for the small rooms, rather than adding heads by room count alone.