The line an in law suite addition must not cross
Whether it has a second kitchen. Orange County and each city define that line differently. A suite with a bedroom, bathroom and sitting room generally counts as an addition. But add a full kitchen and many jurisdictions treat it as a second dwelling unit. That means a different permit and different zoning questions. On some lots it is not permitted at all. See accessory dwelling units.
A kitchenette without a range often stays the right side of that line. However, it depends on the municipality. So we check it first rather than last.
Design for who is moving in
Most in-law suites house someone who will be there for years. That makes a step-free entry, a curbless shower and wide doorways the obvious choices. They also cost very little while the walls are going up from scratch.
Privacy in both directions
Give it a separate entrance. Isolate sound in the shared wall. Then add a door between the suite and the rest of the house. Those three do more for the arrangement working long term than the size of the room.