I use Linux, but it should be pretty straightforward on Mac as well. Just type "R" in the command prompt and check the manpage for R itself ("man R").
I'd also look into the "knitr" package, which is what all of the Rmarkdown is based around. So for instance, most of my Makefiles are based around a simple command like:
R -e "library(knitr); knit2html('index.Rmd')"
Then I just code using VIM on index.Rmd. You can probably set this up however you like with the R command line.
For interactive it literally is just typing "R" in the command prompt. For help, things like "?ggplot", "??knitr", or whatever, so you can open multiple interactive sessions like you were using IPython or something. When you print a plot, it just pops up in a new window.
You can also use "R" to just execute R raw if you are trying to do it without Rmarkdown. I just prefer the HTML output. Pretty sure all the RStudio RMarkdown stuff just calls knitr as well.
The output looks the same as anything on RPubs (and there is a way to publish to RPubs, I used to have to do that at one point), random one from the first page:
