From my understanding "sandbox" features eats alot of pc-power, if there something what changes the world etc. Destructible terrrain, buildable houses etc.
Yeah, of course ! I was more referring to the context of the thread. I think the game performance doesn't go nuts if the creative options are limited in an amount of choices. Like having many features for one's clothing part (like putting your shirt inside / outside your pants, tear the sleeves apart, change color, print a logo, etc.).
Same for your example with the song being displayed on the radio. You could pick up a topic from a list, and lyric bits to choose from. As there are variables attached to them, the song will have a specific meaning, the game would know that meaning coming from it, and NPCs will then react. It's more of a long process and doesn't affect the performance.
On the other hand, I'd find it extremely difficult to mix free city building with a handcrafted map like CP77, if that was your point, even though there's always a solution like in Skyrim with personal home building or even Fallout 4. But CDPR isn't going to let us build stuff, I think it's too far from the game goals. I'd expect vehicle customization and creativity in clothing and crafting "stuff" with the crafting skills.