Can a Channel apply to more than one Program Type?

I typically have two Email Channels named slightly differently. 

Email Blast - (This is for the default type)

Email Test - (This is for the email type)

"the issue is once users create an email campaign under a Default program type, A/B testing is not an easy task (have to do a workaround)."

Depending on what you want to do, I pick Email Blast or Email Test. Personally, I rarely use the Email Blast (Default type) because usually the email is around something like a webinar which would mean the program is for a webinar, or to promote an event which would be more relevant in the tradeshow and events channel.

You can A/B test in either default or email, but there are pros and cons in each. 

You can however, create an email type program within a program which is what I mostly do.  It is nested as a local asset within a program. 

Within a program, create new local asset and you can choose the icon with the mail box and that will do it. 

See Jessica's explanation.