Interesting, these are good use cases to know about!
1) Is there a way to copy all of your data sources from an existing IW model to a new Model Builder model or a new blank model so as to avoid having to go through the process of adding the data sources individually and styling them?
Unfortunately we do not have a way to do this at this time. I'm curious though, if we were to add an option to select data sources in the "Create New Model" dialog that appears when you click "New" on InfraWorks Home, would that address your use case? (I cannot guarantee that this will happen, since I do not develop features for InfraWorks, but I could pass this suggestion to the team. If this is your rough idea, I would suggest adding it to the InfraWorks Idea Station as well.
Also, is there a way to customize IW so that it starts with the same Styles for all projects? In other words, we have created custom styles for floodplains, parcels, soils types, etc. It would be nice if when I create a new model that it just pulls up our standard styles without having to import them through the style catalog.
I believe that you can add custom styles to the InfraWorks style catalog though a manual process that we don't really support nor recommend, although it is possible. Navigate to C:\ProgramData\Autodesk\InfraWorks\Resources\LocalLibrary\Styles to review the styles and add new ones manually. Be Careful though! Messing around in ProgramData can lead to corruption and other issues, which is why we don't recommend this as a supported workflow.
Here is documentation that shows a bit of this process for the purpose of adding new multi-scale terrain texture styles to your Style Palette. https://knowledge.autodesk.com/support/infraworks/learn-explore/caas/CloudHelp/cloudhelp/ENU/InfraWo...
Note: to my knowledge, custom styles will not be uploaded to cloud projects unless referenced in local models before being synced with the BIM 360 Document Management project.
Principal Specialist, Infrastructure