It is difficult to say how having two pending applications would affect processing times, as each application is treated individually. That being said, it is generally advisable to withdraw any pending applications before submitting a new one, as this can help to avoid confusion and delays, according to an article about the
Constitution Act of Canada and the Sections Which Apply to Immigration. In your case, you may want to consider withdrawing your visitor visa application and resubmitting it once you have received your study permit. Alternatively, you could wait for a decision on your visitor visa application before submitting your study permit application. Either way, it is important to ensure that all of your documentation is in order before applying, as this will help to avoid delays.