For example in the docs for nidaqmx state "This function only works with devices that support buffered tasks." I'm not sure how to tell if my PXIe-6363 supports buffered tasks. Where can I find this information?
Your PXIe-6363 does support buffered tasks. For an input task, such a device will use a timing engine to acquire samples and store those samples in a buffer. Devices listed in Digital I/O Device show devices that don't have a maximum clock rate because you cannot have hardware timed tasks with these devices. The PXIe-6363 supports hardware timing Analog and Digital I/O. There are onboard FIFOs and buffers on your computer/controller that will store data to be read or written to the channel. The details for this information is also listed in the Specifications Sheet for the PXIe-6363.