Footprint accuracy is paramount. The best assurance is human backup.
Can third-party libraries be trusted? This question arises occasionally during design team meetings. Third-party libraries are default libraries in the library tools, the standard libraries included with design software, and any libraries provided from a customer or vendor.
Constrain what is necessary, but don’t go overboard.
Back in the printed circuit board’s early days, before EDA tools were even necessary, constraints were handled verbally. The engineer would carry the schematic to the PCB designer and concisely state the constraints: “Can you fit this on a 4x6" board?” That’s certainly not the best way to communicate constraints, although I would guess there are instances when the design still needs little more communication than that.