Broadcast legal levels for the major streamers?

[David Cherniack]

I'm about to start developing a highly stylized look for a project in Resolve that will depend on very saturated elements in the frame. Coming from a deliverables for broadcast background, I'm new to the world of HDR&SDR deliverables to the streaming giants and while I will be working in Rec709 for practical reasons, I'll be taking the film to a Resolve facility like Technicolor for final grading in HDR and SDR formats and deliverables. So I'd prefer not to create a look with chroma levels that have to be pulled back to the point where they hurt the creative intention. I'd rather know what I have to deal with right off the get go.  But when I research this topic I can't seem to find any definitive answers on what the Streamers expect on Chroma levels. I don'tsee, for instance,  in the Netflix specs, any mention of chroma levels. So some rather puzzling questions:

Are the HDR streamers changing the longstanding (antiquated?) QC parameters of broadcast safe?

The Broadcast Safe switch in Resolve apparently may create issues and may not be applicable. Is the gamut limiter plugin a good option for rough control of chroma limits?  Should it be set to rec 2100 even though my grading will be done in 709?