"Was thinking about this today a little and I realised that up high you wouldn't be EGT limited but RPM limited instead"
don,t think that much . it depends on the type of engine. and of course a turbofan can be EGT limited- i.e the ALF502 on bae146- we set the power according to EGT at cruise , that came first, not the permissible n1 or n2 rpm,s .
on a turboprop it also depends on the engine, even from the same family, one example :
the pt6a-11 on a cheyenne I is definitivly ITT limited at altitude , the pt6a-41 in a cheyenne III is gas generator speed limited at altitude .