Above models have been produced from photos or existing 1:87 kits.
Sketches, rough mocks are created before the final product as above.
Stiff cardstock is available from art suppliers. There are many types to choose from.
Tools required are pretty basic. Exacto knife, yellow glue ( not PVA ), pencil, tweezers, scale ruler, etc.
Building in cardstock can be quick, fun and extremely CHEAP.
Cladding, roof, doors, windows, paint, details - modelers choice.