The short answer to your question is no. You can't upload your project without building it first. I mean, when you build the project the IDE compiles the code and create the file or files needed for the script to run on your board. Meanwhile when you upload the project you are only sending the files to the board. If you hit the upload button before building the project then you will probably upload a previous version of your project and if you have made changes to the code they will not reflect on the script.
The "XDK IoT edition" uploads plain text .js files to the Dev Board, there is no compilation.....what are you talking about exactly? I too would like to know the difference between the 2 buttons in the XDK.