@Nps For the record, I’ve seen arguments that a hybrid system has benefits (DOI:10.1007/s10797-012-9214-3, mainly p. 12–13), but there’s a lot to it and I’m not taking a hard position myself here and now.
@yaboi69 the ETS has a price cap after which they release extra credits, as well as a price floor, so it's arguably already a hybrid system. If it hit the price cap and stayed there, it would arguably be functionally equivalent to a tax.
Does the New Zealand Emissions Trading Scheme count as a carbon tax? https://environment.govt.nz/what-government-is-doing/areas-of-work/climate-change/ets/
@B I don’t think it should (unless it’s a hybrid). They are both forms of carbon pricing, but they are different in important ways (predictable emissions vs. predictable prices).