Rekordbox Contract Plans

Yes, you would need Creative or Professional plan to have full access to cloud library sync. 

Please see in the link below:

https://rekordbox.com/en/support/faq/library-sync-6/#faq-q600155

What confuses me is the part "cloud option" i also could add to a free plan.

see: https://rekordbox.com/en/plan/

In the FAQ is this mentioned, but only for a dropbox account ...

I dont need dropbox since google drive also works.

Same thing still applies on the Free plan

You can upload and sync up to 10 tracks that can be added to the [Trial playlist - Cloud Library Sync], which is a playlist for sync.
Please note: The entire library will not be synchronized.

I recently bought a DDJ-FLX4 and when i plugged it in rekordbox i only get the free plan, Any help?

That is normal. 

As hardware unlock device does not mean it activates a paid plan. 

Hardware unlock basically means it is a plug and play device. 

So while controller is connected you can use it with rekordbox.