Great post!Believe it or not, I seem to get some of those differences in modelers when set to emulate some of those simple amps (by simple, I understood you meant Class A amps like a Champ, sorry in advance if not the case). In any case, it is one thing to go from clean to a 5e3 mean; a Recto will not go from its clean to its meanest through touch alone. The GOOD modelers today are at least bridging the gap in regards to those variations in tone we get from simple tubes (I own an Acedo Audio 276, basically a Champ with a EL84 power tube, so I know and love those too!). As for a Recto that goes from clean to meltdown, now THAT would be an interesting direction for digital, exactly because it can't really be done with tubes. If I'm not mistaken, the Litigator amp in the Line 6 Helix does something of the sort
By simple I don't mean Class A, though some class A amps fit the bill.
My definition would roughly be: 6 knobs or less, ideally no master volume. That covers most classic fenders (count one Channel on a blackface), voxes, Marshalls etc.
A champ and a 5E3 do definitely qualify - a reason this is important to me is a decade gigging a Victoria double deluxe -pretty much the last word in touch sensitive.
Your point about models following the Amps is interesting -i definitely wouldn't be seeking clean to mean with just a pick out of a recto.
I'll go and have a play. I recall my helix 5E3 doesnt match my Vic for dynamics -but I haven't compared for a while.