Is there a way to not reinvent the wheel? If I already have tests and quizzes made, can I simply upload them or do I have to cut and paste each individual question into Canvas?
If you have a test generator, such as Respondus or Examview, you can convert the word document into a QTI file following a certain converting format. Then you can import the QTI zip to the course. Make sure you are using QTI 1.2 and above if the quiz is made with Canvas New Quiz.
There are some free converters online such as BrightSpace etc.
Otherwise, you will have to reinvent the wheels.