rendering adds silence?

You can turn this off in your settings - not sure how without Reaper open in front of me, hopefully somebody will chime in. In the meantime, you can select the entire project (since all the tracks are the same length) and set render to "time selection" instead of entire project. This will eliminate the two seconds or so of silence at the end.

What do you have set up in Preferences/Audio/Rendering, Tail length when rendering project or stems, or freezing tracks?

The added tail length is there to let any reverbs ring out at the end of your track. Obviously these will continue for a short time after the audio files themselves have finished playing. Without this the reverb might get cut off before it has finished "dissipating". As has been mentioned, this is an option and can be switched off... >

Hi folks, please have a look here: