API Plans & Limits

Hi HeyGen team!

I'm currently on the Pro API Plan and have some videos stuck at 95% ready for over 24 hours.

Please can someone clarify:

Do "priority processing" limits apply to API plans or only to "unlimited plans" and they do apply, how many priority processing slots on each API plan?
How many videos can we process at the same time on the Pro API plan and Scale API plans?
I'm interested in upgrading to the Scale API plan but I am concerned with whether it has priority processing limits, please can you clarify?

Thanks!

Mike