I guess the Sport in Eco mode is as close to Premium as you're going to get. I think in general that the fit and finish will be pretty similar between all the models, but options fitted as standard (IYSWIM) may well be somewhat different.
Ah, and I expect that the max regen won't be as strong on the Premium because there is only a single motor to do the regen. So presumably on this argument then the max regen will be highest on the Sport Plus, with the Sport being intermediate between Premium and Plus.
I see there is at least one Premium review on YT: