For anything higher strength psi I would use the highest reference psi available. Higher strength generally means higher impact, which means it will be harder to show any reduction. If you don’t see a reduction, then just use your actual mix for both baseline and design cases. (This would be true at least in GWP as shown in the study used for the development of the Low Carbon Concrete Code in the Bay Area - this is a screenshot from a webinar, so i don’t have an exact link to the source).
For shotcrete and high-early strength concrete I am also not aware of any regional baselines, so EC3 might be your best bet. High-early by definition has higher cement content so it’s not very carbon-conscious in the first place, since you would normally look to lower your cement content and use SCMs that typically slow the time to strength. In that case I wouldn’t claim any reductions just as in the other scenario, unless someone proves me otherwise. I am not too familiar with shotcrete, so again, better not claim a reduction that claim a bogus one.