Its a bell curve if you can plot these things numerically. You need a certain minimum of power to be able to obtain a creative application.
Take the standard Fighter for example, his sole option is to hit hard. For other things he simply does not have the resources to creatively exploit, no acrobatic stunts or improvising scenery because of inadequate skills. 'Creative' solutions here are engineered or fiat solutions, you have to specifically build these solutions into the problem, so they're more like puzzles than actual creative processes.
On the other extreme, take the prepared caster. Yes, they have the resources to be extremely creative(most of the open ended spells really), but at the same time, they also have an enormous golf bag of perfect solutions. So they have no need for creativity or improvisation, you don't turn into an ant, crawl under a bolted door and open it from the other side because you can just teleport past, magically open it, or disintegrate the door entirely.
So for maximum creativity, you'd need a small number of open ended abilities with relatively weak linear power, such that solutions cannot be easily brute forced, but always accessible.