In most cases training and development delivery is most effective when using a 'blended' approach; a mix of both 'live' (synchronous) and 'in your own time' (asynchronous) learning.
The 'live' elements should be relatively short, focussed, and be participatory. Sessions would typically be approx. 1 hour, but longer sessions (max. 2 hours) with breakout rooms can be a valuable way to connect with participants. Synchronous learning is a great opportunity to engage with participants in discussion, feedback, Q&A, and can help to build a sense of community and belonging. Depending on the depth of the course, you may wish to run one or multiple synchronous elements.
The 'in your own time' elements should prepare learners for, or provide a follow-up from, the live elements, as well as giving an opportunity for independent, collaborative, and active learning. Asynchronous learning can be spread over several days or weeks.