Duke William of Normandy won the battle because was well prepared and had a good army. They prepared carefully for the battle. The Normans had knights on horseback who were skilful fighters.
A utility knife, metal ruler, and a hammer can be faster than trying to carefully saw an opening. Score the drywall a couple times till you are most of the way through, then just knock a hole with the hammer and break the drywall back at the score lines.
You can cut a hole in drywall without any issues. When your desired hole is larger than the stud cavity behind that drywall, that's when you will start needing a professional to determine if that wall is loadbearing. You will need to install a header and jack studs to carry the load that the wall carries.