Heroic I think can be a scale OR a tone as two different things I think @Aebir-Toril hits on that very noticeably in contrast with your comment or not exactly but sort of.I prefer tiers of play.
Then one of the best in the village
Then one of the best in the city
Then one of the best in the country
Then one of the best on the plane
Then one of the best on all planes
Scale and tone are two different things but can be connected.
Its like if your character is authentic Cu Cuchulain of heroic to epic scale they would also be a pile of grim story wise but huge grim.Scale and tone are two different things but can be connected.
My point is I prefer all of the tones. I like my level 1 grim horror, my level 10 heroic action, and my level 20 shonen anime.
I'd probably be a bigger fan of this model if the dm's I play with don't immediately get disinterested the minute the pc's do anything heroic, and start talking about resetting to zero.I am a fan for the zero to hero model. I feel having that early campaign part being more realistic and gritty helps set the proper contrast for when they gain in power and become heroic. It's like that saying, you can't really appreciate something fully unless you know what it's like without it. Additionally, it provides different challenges from the start of the campaign to the end of it, where many problems are easily solved through magical means. It keeps the game from being the same thing over and over, IME, when the players have variation of problem solving challenges rather than "super power" for everything.
Tone isn't necessarily linked to power level. The Black Company is grimdark but they still deal with ridiculously high powered threats, while a bunch of first level clerics and paladins would still be Paragons of Virtue, chasing off goblins and rescuing minor nobles.I will say i think starting in the level range you like say i like 5 to 15 and double the time that we spend in those levels always seemed to be a good solution to tone change,