Upgrade from 2.1.1 to 4.0.0

Have skipped a few releases and plan to upgrade from 2.1.1 to 4.0.0.
Can I use the current model settings, or do they have to be adjusted?

Of course I will check them anyhow - one by one.
But has any of you a hint / experience, if something needs to be changed?

Thanks in advance.