Hi Frank,
>Is it possible to import the App Intentor code in a MobiOne app project?
No
> Is there a easy way to visually program tasks like string list handling in MobiOne? Where can I get some code examples?
Developers of MobiOne HTML5 apps use JavaScript to implement their custom business logic. There are tons of online references and how-tos for almost every type of web programming problem.
> Is there a easy way to read a Google sheet with simple SQL statements (like using the Web component in AppInventor)?
Not at this time. We have built apps that use google docs but they used a webservice api.
>Is the execution speed in the compiled MobiOne app at the same level as an app developed in f ex XCode?
MobiOne apps are HTML5 apps implemented in HTML, CSS and JavaScript. XCode is used to package the web content + a webui browser component into a native binary. The popular Cordova/PhoneGap platform is provides the runtime implementation.