The difference between ATPL and CPL in brief:
CPL – Captain in General Aviation
CPL – First Officer (co-pilot) in an airline
ATPL – First Officer (co-pilot) in an airline / Captain when 1500 hours of experience
The modular courses offer the opportunity to get licenses and endorsements (ratings) in parts. The theory only will be given in classrooms, but nowadays distance learning via the Internet is also available. The training is divided into modules which are classified in accordance with the candidate and the school. So this training can be combined with other activities of a candidate.
The contents of the modules are fixed, but the duration of the training depends on the frequency of flight lessons. You have freedom when going through the modules, but you must take into account that there are restrictions based on the validity of obtained intermediate exams required for the license.