I just had a couple of questions. Anytime I import a piece of Alexa footage (most recently a logC 422HQ piece of footage) into my viewer, apply the LUT(filter) the video plays back choppy. It played back just fine in the view before I applied the filter, but afterwards it slowed down on me.
Play with your timeline's RT settings. Turn off live video playback to the scopes. I've found that you have to change the frame rate/quality to Full and High and then it's OK on an 8-core or 12-core Mac Pro. In fact, I'm currently working a a 2-camera Alexa edit. ProRes 4444 Log-C, 1080p/23.98. I have a "selects" timeline with both cameras side-by-side (so PIP scaling on V1, V2), plus LUTs applied to each and sync'ed, merged double-system sound. Everything plays back well even though it is unrendered (orange bar).