Microsoft upgrade guides
Surface Laptop, Pro, and Studio — mostly sealed RAM, SSD varies by model.
Surface Laptop 5 (15-inch)
Consumer Surface — RAM soldered, SSD replaceable on some service paths.
Surface Pro 9
Tablet with keyboard — soldered LPDDR5, SSD behind display (service difficulty).
Surface Laptop Studio 2
Creative convertible — soldered RAM, removable SSD.
Surface Laptop Go 3
Budget Surface — soldered RAM, SSD behind bottom cover (difficult).