I'm not sure I really understand your question, TI-84 (and all other TI models) don't use RPN. You can run a program to allow RPN input you want, since most of the higher TIs are programmable. I believe some of HPs current lineup have a limited RPN mode available and SwissMicro makes some new RPN calculators.
>I took an exam today where only TI calculators were available.
That's common as they are the ones used to teach math classes and are vetted to prevent cheating on standardized tests.
>I felt I was caught between some older models where the TI interface was not quite worked out.
I have no idea what this is supposed to mean.
>And I don't see much progress then trying my daughter's TI-84.
Nor this.