There is also Blick which launched recently which claims to be very very fast https://blickeditor.com/?lang=en and part of recent wave of fast software (Task Slinger, File Pilot)
The fact that they reimplemented everything from scratch doesn't give much confidence. The last thing I want to deal with in a video editor are bugs from code that's seen less real-world use, originating from who knows where.
Neither open source nor free however.