I have a problem whether to have everything in one modal, or have one after the other. Any help would be appreciated. Please pic the option that makes sense. Any other solution would be awesome too :)
I’d choose option 2, the “wizard” pattern.
Your second option allows the user to digest the UI in chunks and maintain comprehension of that screen until they are ready to progress.
If a significant portion of your UI changes, it can cause the user to have to reprocess everything to evaluate what just changed if they weren’t paying close enough attention.
Using the wizard approach, you hide the details of “well you picked option 2, so BAM! here’s more fields to complete.” Picking a value in a drop down is not a typical trigger to cause a significant UI change, so it will likely be unexpected. Isolating these dynamic fields will make your application appear more fluid.