Why am I locked into a Rec709 timeline? Can I not work in the Rec2020 colourspace my camera captured the footage as?

When I import CLOG2 CinemaGamut footage from my Canon C300 MKIII and then drop it into the timeline is it converted from Rec2020 to Rec709 color space automatically? The timeline is locked into Rec709 and it cannot be changed for some reason. I choose not to convert my footage with the Canon conversion LUT provided from Canon but rather use a third-party LUT to do that. The issue is that "Custom LUT" has conversion options, input and output. Rec2020 and Rec709 to pick from. Which one do I use since the footage was shot as Rec2020 originally. If it is already been converted to Rec709 in the timeline does that mean no conversion is needed? Sorry lots of questions but I could not find information on this after searching every site I know. Not sure why this has to be so confusing but it is.