You professional field does affect to the point you get, under the regulation of immigration criteria. The visa officer only recalculate how many points you get under the criteria.
If you work out an amount of points exceeds 70, that's ok. The visa officer will get the same result, if no mistake happened in your calculation. You can do anything after you land in Canada and you don't have to explain it to the visa officer. On the contract, if you have chance to talk directly to the visa officer (during an interview), you should appear having great confidence on obtaining a good job in you field here.