I love player initiative
I think the line between helpful flavour and godmodding lies in mostly in detail, partly in agency - a character plonking down a mid-village tree or a forest where there wasn't one before would seriously trip me up narratively and bring the game to a screeching halt as I rearranged everything or pulled them aside for a Talk, because being highly aware of how landscape shapes communities, that's a lot. If I'd already said there was a forest and they said they liked the light off that pine tree, or the oak they first kissed a barbarian beneath, or went to chase some local squirrels, all that is welcome (so long as a setting isn't based on one continent's ecology and no-one dumps lions or raccoons in a Standard Quasi-Mediaeval European setting. Tolkien's Magical Potatoes get a pass, but only if noted as such, and only just).
As for agency, thumb rule is "am I 100% sure this is a universal reaction, or is it an NPC I know well enough to be certain that's how they'll react?" Someone having their head cut off in battle reacts very predictably, for example: they try not to have their head cut off, but then their head gets cut off and then they get a career change to corpse and fall down. Declaring everyone in the tavern finds you attractive and laughs at your jokes, however, that's something that takes decisions away from a bunch of NPCs - if the PC has crazy high Charisma you can declare that intent, sure, but that's at least a roll needed. It's super easy to ask the GM before doing that kind of thing, too, as praguepride's players seem to be good at - "will the barmaid flirt back and giggle?" for example; if the answer is "no, she has a wife and a large dog and doesn't feel the need to do that. She likes gross jokes, though, and has a booming laugh", it provides the interested player with a point of interaction with a more interesting NPC, and if they want to flirt with a giggly person the player can still ask the GM where those hang out.
In fact, you could probably summarise here as 'finding a giggly redhead in a pre-existing nonspecific crowd' = flavour, 'declaring a specific NPC is giggly/ginger without GM input' = god modding. Same for props or setting details. Finding a stick in a forest is fine, declaring the specific stick is a seasoned hardwood branch that happened to be to hand during combat...ask.