When your quality gate fails what is the default? Does the pipeline completely fail or pass? Which is recommended to do?
Welcome 
there’s no default, you may do an analysis without considering the quality gate.
IMO you should always check the quality gate status and fail your pipeline if status = Failed.
Does it make sense to deploy an application if it has bugs/code smells … ? No.
Even if it’s still alpha, your code should be clean from the start.
Ignoring bugs or code smells at first for being quicker (time to market … bla bla) will result in technical debts and problems later on.
Assuming you’re using a modern CI/CD build there are different ways
for Jenkins see
for others see
Gilbert