Hi,
Welcome to the RStudio community!
I'm not an expert on the server parts, but if you like to have a Shiny app run for multiple users, it's better to use ShinyServer. In Rstudio, you can access the same running Shiny app multiple times, but it will all be run on a singe processor. If you have an app that requires a lot of CPU or memory, this will be inefficient. Shiny server can use multiple CPU's to run (I'm not sure if the free edition can).
Another important thing to consider is optimising your app to make sure there are no redundant calculations or memory allocations when multiple users are working. Look at the scoping article for more info.
Good luck
PJ