http://jupyter.org is an alternative to R. Same, a bit of a learning curve, but the sky is the limit.
As far as I understand, Jupyter is a front end to multiple data analysis languages such as R, Python, Julia. I see that they even have an example of using C++. Most R users use RStudio as an IDE / front-end, but Jupyter is also popular. I use ESS (Emacs Speaks Statistics) which is far less popular.
As for data size, I often have 100 million, or more, data points in my R session. These data points are usually first loaded from csv files (actually space separated) but then stored in a R binary format for faster re-reading.
The OP may want interactive graphics. While there are many ways of doing that in R, most now use JavaScript for browser display. I'm not sure how well they do with very large data sets. Making static plots from large data sets in R, with panning / zooming / etc, is straightforward from the command line. Doing it via mouse is more work.
I'll also note that my presentation referred to above includes some crude SCPI control and data acquisition in pure R. I expect to do more of that in the future.