@EmmettCrass -

Unfortunately, having Canvas do it for you automatically is not possible.  That is you cannot set the grade for a quiz be 6 points when 7 questions worth 1 point each (answer 6) is provided.  With Classic quizzes, what I would do is create a quiz with the questions(and their point values) and tell the students to pick which ones they want to work.  Grade the quiz.  Then create a separate quiz assignment with the points possible (i.e 6 for a 7 question quiz choose 6 to work with each worth 1 point).  Then copy the actual quiz grade over to the quiz assignment grade holder.

The above works well if you are using weighted gradebooks.  put the actual quiz in an assignment group worth 0% of the final grade and the quiz assignment in the actual gradebook part.  

For a points based gradebook, you may have to select the quiz type as practice ( I am not sure if that would work, but it would be easy to check)

For new quizzes, there is a possible way to set the point value of the quiz different from the points available on the questions (not 100% sure, but I have seen something to this effect, I know how it was done, but I am not going to put something down that may not be correct.  Plus I believe it requires absolute perfection in creating the quiz - that is you get one shot of setting it up and if you edit it after setting it up you lose the point total being different from the question totals.  I may be wrong as I do not use new quizzes)

Ron