Create a simple floor map
Mark the router/access points, main work/streaming areas, floors, dense walls and obvious obstacles. Note where devices actually need reliable service rather than trying to maximize signal in unused areas.
Measure consistently
Use the same test device and roughly the same position at each location. Record band, signal indicator, throughput and whether problems are consistent or intermittent.
Check node backhaul
A mesh node can show strong signal to your phone while having a weak wireless link back to the main router. Test the path through each node rather than judging only the client-to-node signal.
Make one change at a time
Move one access point or change one topology variable, then repeat measurements. That makes it clear whether the change helped instead of creating a new unknown configuration.
Networking capabilities vary by hardware, firmware, ISP, country and radio environment. Settings names differ among manufacturers, so use your device's current documentation for product-specific changes.