Moving users from K1 to E1 Plans

We are an System Integration Partner.

I have a customer who has to move his existing 600 nos of K1 Plans on the Cloud to E1.

I understand that we now have an automatic option to Switch Plans from the admin console.

I have 2 questions pertaining to that 

a. Is there any limitation with respect to using the Switch Plan option in the admin console ( eg: only works if the no of plans are less than 300 for example)

b. If we have to do this migration 'manually' - is there a procedure listed for that to occur

Your inputs would be really appreciated

Ajit Andrew Mohanraj