I would always assume most deadlines are strict in the application process especially considering so much is automated these days. Conflicting deadlines is one of the challenges of the process especially when you're applying to diff program types. Since this is very much a school by school and case by case decision I would reach out the schools for guidance and inquire if they're is any wiggle room if not you may want to prioritize your application strategy so you can minimize the amount of difficult decisions you have to make.