Well, what I've seen the most is people replacing objects or even people using AI-assisted tools. Personally, what I've used the most is CapCut, basically to edit real videos, add subtitles, remove backgrounds and things like that.
It even has a pretty good tool to replace objects or put your own face on the person in the video, although that last feature doesn't work very well.
They also have some pre-made scenes that you can use as templates.
Capcut is not expensive, you can find new account for less of 5$ / month.