If you can afford to fine tune those types of things on a 273, they'll pay bigger dividends on a 408. This is exactly what I mean when I say 'all things equal' - it means equal effort.
This is why your premise of 'the same parts' isn't useful in any case. What works for one is rarely the right choice for the other. The same level of effort though will reap greater power with a larger displacement.
Also, most hot rod parts are going to favor more cubes anyway. Building a high RPM screamer takes a more bespoke approach. It's not impossible to win with RPM, it's just not the type of program which can be described in a forum post.