I haven't used all the APIs you mention. I can only tell you what my own experiences are.
Creo Toolkit C
This offers you the most low level access to PTC Creo data.
It allows you to create features, change features, ...
It allows you to create an independent GUI with the APIs provided within Toolkit or you can use whatever you want what you can use with C
J-Link / OTK Java (Free)
This offers you access to PTC Creo data but not as low level as Toolkit.
It allows you to change features but you can't create new features directly like you can with Toolkit. You can partly circumvent this problem by using User Defined Features (UDFs).
You can create an independent GUI with whatever you want what you can use with Java.
Web.Link
This offers you access to PTC Cro data but not as low level as Toolkit.
It allows you to change features but you can't create new features directly like you can with Toolkit.
You can create a webpage that acts as the GUI and that runs within the embedded browser of PTC Creo.
There is a free thirdparty toolkit Creoson that can help you developing Web.Link, JLink applications or applications using Python.
http://www.creoson.com/
Best regards,
John Bijnens
YouTube channel: https://www.youtube.com/@jbijnens
