Main question is : Am I right in thinking that any client websites using Adobe Fonts will need their own Creative Cloud account in order to continue using them after Dec 31st 2019? 
This doesn't seem ideal - is there no other licensing option? From reading old forum entries it seems like their used to be a "business license" on Typekit which allowed agencies to use Typekit fonts on client sites.
I have many smaller clients who don't want to be managing licenses for multiple things and just want me to look after it all - I can't imagine they will be comfortable with needing a Creative Cloud account.
How are other agencies / design companies handling this issue?