I haven’t done this, but by creating a custom code it can return the list of adaptive forms from the forms content path or if the forms are listed on the forms portal, from there I think we can also retrieve the list of forms.  https://experienceleague.adobe.com/docs/experience-manager-65/forms/publ...

You can give left, right, top, and bottom margins in the subforms as per your need.

See the images of how I changed the highlighted to flowed and wrapped the positioned subform inside the flowable subform and it worked.  

Have you made the Main page flowable and allowed pagebreak in all flowable subforms and on the main page?   If it still doesn't work, share your form. I'll look into it.

Can you please check if you are missing the mentioned bundle in your AEM instance or using the old version incompatible with the code? Please verify the bundle and update the version or code accordingly as per your environment.

Yes, that's the case with the positioned layout. You can do one thing if you do not want to change every subform to a flow layout, then let it be positioned and wrap them under a subform with a flowable layout.

Yes, it will jump because you have made others as positioned. So make other flow as well. It will be good for future changes, if you need to add/delete any fields in the future then the flow layout is best, it adjusts the form itself. 

Use the flow layout for the Main page and for the subform if any are used in the form. Also, make the field expand to fit and make it multiline from the field property. 

Here you go! https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/forms/integrate/services/embed-adaptive-form-aem-sites.html?lang=en   Ensure that the AEM Form component is configured as an allowed component in the associated template in an AEM sites page.

https://stackoverflow.com/questions/74435561/aem-forms-adobe-form-submission-failure-on-publish-instance-error-code-aem-af   check this out, please.