Main difference between Authorize.net and Authorize.cim regarding payplans is
Authorize.net process the notification once in a day. So, you should wait and check whether subscription get activated or not in a day.
While in authorizecim, we get instant payment notifications regarding payment.
So, if you have recurring subscription, then it would be better to use authorizecim, in order to get instant notification or if you still want to use Authorize.net, then set "Wait for payment". You will find the "Wait for payment" option in the payplans configuration, under the expert tab.