I've done about 10 church shops for Faith Perceptions. I was paid within two weeks on all of them.
The questions I had to answer had no religious connotations. They were based on a first impression of the service and the church. I could have attended just about any type of service or denomination and the questions would have applied.
All the churchs I've attended have about 75 to 125 attendees. That hardly puts them in a Megachurch status. I'm sure the Mega's do their own shopping.
The emphasis was on how welcome that church makes a newcomer feel. I can see that from the perspective that churchs tend to become a closed club and they should be more open and inviting.