Is there a limit to the number of response sets you can have on a template?

It is not a hard limit; instead it relates to how big the data area containing all those sets becomes, which is a factor not only of number of sets but of number of fields in each set. The entire group of sets has to be delivered to the client (the proof in the buyer's web browser) in one big data transfer. Complex templates with dozens of fields would hit the theoretical limit sooner than simple templates with just a few fields. In general, if you exceed 200 response sets x 50 fields, you should start to worry.

The response set editor in eDocBuilder admin does not have a limit (and doesn't know about the possible data limit mentioned above). As a result it will not prevent you from creating any number of sets and it is up to you to exercise caution regarding the number of sets and fields.