I have done quite a few long form projects with 5 timelines and hadnt had problems.
I like to quickly show clients different parts of the movie if they want to see anything particular…
You just have to have only the media that youll need in the browser. I would use a folder for each timeline.
Don’t use a clip from different folders otherwise youll get those crashes pretty soon!
I would grade in Rec709 Gamma 2.4 (its standard, not 2.2!!) because you can calibrate that with your current monitor.
The XYZ conversion does usually the house that makes the DCP just tell them your Settings (Rec709, 2.4 Gamma, RGB colorspace) so they will do the correct conversion to DCI P3 XYZ colorspace and Gamma 2.6.
lee