Hi Erik,
the ACT100 covers the SAP Activate approach holistically. You can review the course structure on ACT100 - SAP Activate Methodology | SAP Training and Certification Shop
The general structure is that we first cover the methodology fundamentals on example of S/4HANA and then go into project journeys for following scenarios:
1. New implementation in cloud (S/4HANA cloud editions)
2. New on-premise implementation (S/4HANA on-premise edition)
3. System Conversion to S/4HANA
4. Landscape Transformation to S/4HANA
So technically if you want to learn only about cloud implementation you could attend ACT100 and decide if you want to stay for the on-prem, SC and LT journeys. When I delivered this course in first teach the cloud topic is completed by early morning on second day of the training.
Jan