Hi Eric, welcome !
NTRIP is required for real-time applications only, not for PPK.
NTRIP is a protocol that allows to stream GPS corrections through the Internet. The rover has the role of a NTRIP client, retrieves corrections by NTRIP, and is able to compute its precise location in real-time this way. Very convenient to record GCPs 
Recording GCP locations in PPK with a single Reach RS2+ is a bit tedious in my opinion. In PPK you always use 2 receivers : 1 as the rover, 1 as the base. You have the rover only, so you have to find a public base, aka CORS, if some are available in your area. Then, you will get the GCP coordinates after a post-processing operation, for example with Emlid Studio. If your data was not good enough, you will see that the accuracy is not good only at this moment, and not in the field, which can be a problem.
Having a second receiver in your own hands may be very useful, and the workflow is pretty nit ā How to correct collected points with a new base position? - Support tips - Emlid Community Forum