Anything that is "tossed" in advance when working with any ProRes will be completely imperceptible. And if you upload it as HDR, anyone watching it in SDR—which will be 99.998% of viewers—will see it with a different tone mapping than you, so different than you. And "full colour gamut of DCI-P3" is irrelevant in video because it's a digital format for theaters and is useless for Youtube. Never mind that that could even only be relevant if you somehow assume that everyone watching the video even has a screen that can display it, which carries just about the same percentile likelihood as above. You are WAY overthinking matters.
And since I have no clue what export options Photoshop—which is not a video editing app—has, I can't tell you what to output.
If it were Final Cut Pro, where you wouldn't have to think about any "conversions", I'd say simply use any "Apple Devices" preset and switch it to "HEVC 10bit". That will give you a 10-bit file while still being small in size. What Youtube ends up squishing into quality-wise no one knows. It's not a platform for high-quality content, to begin with!