What you are paying for with Topcon, Trimble and Leica is the their cost of their software ecosystem. There are many integrations with other softwares as well as machine control which is pretty limited with Emlid unless you are willing to do some technical work and purchase 3rd party equipment.
We have been running the RS2 corrections via NTRIP for about a year now and have very rarely gotten out into areas where either cellular service is unavailable or the CORS is too far away. That said Texas is a pretty big state so our network is a little sparse in comparison to what smaller states have and our network is not free but the $2k a year we pay is paid for in about 3 months by cutting base station management alone. Everything else is icing on the cake.
As far as accuracy there is really no difference except for the fact that you either have to have a known point or do some work to get a base point. NTRIP is turned on and you just go within about 5 minutes.
We also use the RS2 as a rover for GCPs and occasionally site stakeout but we have survey crews that do all the layout. We just check in with the Superintendent and help out if needed. For providing corrections to an RTK drone NTRIP is the way to go as well. The alternative is to cast a local base station which I believe people are having trouble with on the DJI products.
Last thing i’ll say is that because we do stakeout and sometimes need the project CAD linework we had to go with a more capable software so we chose MicroSurvey Fieldgenius for Android. It also allows for localization (calibration) of jobsites which is common in construction because there are always points that don’t match the CAD/Plat within our tolerances so the localization prorates all that error as a network.