the build tools 141 means VS 2017, so it will not work with VS2015 and you dont need it, it is all ready for VS 2017. I have been using VS2017 for quite some time and everything works just fine.
Uninstall all versions of Visual studio and start again, the instructions are good. You don’t need to run ofApp.cpp at all, you need to use a visual studio project as it contains all the libraries linked correctly. There are plenty of examples in the Visual studio download and they will all work if you follow the directions. You can skip the plugin part in the download directions. But the heading is in a strange place on the page, make sure you do do this part
" Before you’re able to use openFrameworks with Visual Studio, you have to have Common Tools for Visual C++ 2017 installed, otherwise you’ll get an error message later on. To install, go to File > New > Project and choose Visual C++ in the installed templates section. There now should be an option to install the tools, if they aren’t already. Select it, confirm with ‘OK’ and follow the instructions."
Just install VS2017 as directed by the OF installation instructions, download the VS version of openframeworks, unzip it somewhere convenient and don’t move the subfolders around in there, they need to stay the same. Then go to one of the included examples and open one of the visual studio solution (sln) files to see how things work.
If you need you can use the project generator to make new projects.