Difference between 16+\18+ age ratings?

I’m trying to understand the various age ratings for content on the roll but I’m slightly confused

It feels like 18+ content is much more tame than most 16+ content

I see way more ecchi style content in 16+ content that is WAY more graphic and pushes sexuality to the limits with defined drawings of parties and creases and body contours etc

18+ just seems to be more mature dialogue but less spicy video