My favorite editor of all time is kdenlive. It works really well, and the development has improved greatly the last couple of years or so.
Here are some of my tips and tricks for this editor.
Rendering Options
New ones with lossless setup: -preset ultrafast f=mp4 vcodec=libx264 acodec=aac crf=0 ab=%256+'k'
Tip, set the crf rate to be 17 or so if you want manageble file sizes. 0 is lossless.
Old ones for reference: properties=x264-slower f=mp4 vcodec=libx264 acodec=aac g=120 crf=%quality ab=%audiobitrate+'k'
Speed options:
preset=slower