You can set Layout Type as part of the template.
My assumption is that if it isn't set, they get the default layout.
and now I see the rest of your question - any way to update task templates en masse? that I don't know...
Correct, need to update about 200 Task Templates so I am hoping it can be done.
You could do this via Dataloader, you would have to do an export from the Template Object as well as the Template Field Info Object and update the data accordingly.
Eric J Cobb