Projects by your regular customers - "My Work" - will get top priotiry and you will need to complete them first. In addition to those, and in your spare time, you will be able to take OHT projects by other customers independently.
No, this is not the motivation. The main motivation is to improve quality and reduce translators' "project-chasing stress".
As you know, full-time engagement with select specific customers improves quality over time.