I already have Acrobat Pro software installed on my computer. Are there tools/options in the online Acrobat Pro subscription that I would not get by simply supplementing the software with a Forms Central Plus subscription? Also, with the online Acrobat Pro subscription, can non-fillable pdf's be imported to create a new fillable form?
Access to FormsCentral is available with an Acrobat (Pro) Plus subscription, along wit several other tools: Subscription Options | Adobe Acrobat Pro
Acrobat Pro has an automatic field detection feature where it adds fields where it thinks they should be placed. Importing as you suggest is not a feature of FormsCentral.