You'll need to give the Service Account access to read the information you want Splunk to be able to collect/access. It only needs read rights.
2016 server is still unsupported at the moment, but support is coming soon for the UF. The apps themselves are on different release schedules, so I suggest holding off on that unless you want to beta test in that environment. I have a 2016 server with 2 DCs that I plan on loading it to...just haven't gotten to it yet.