Various solutions for processing timeline enhancement with respect to user equipment and network apparatus in mobile communications are described. An apparatus may determine whether a latency requirement of a service is less than a threshold value. The apparatus may use a first processing time capability to perform a transmission in an event that the latency requirement of the service is not less than the threshold value. The apparatus may use a second processing time capability to perform the transmission in an event that the latency requirement of the service is less than the threshold value. The apparatus may apply a scheduling restriction/optimization to perform the transmission when using the second processing time capability.