Since online teaching is currently THE ONLY option available during lockdown so we really cannot comment whether it is useful or not. It is very useful in the current circumstances but I prefer in-person teaching and learning to a total online interaction.
The use of tools depends upon the level of the course, the interest of the students, access to technology, and a reliable internet connection and institutional support. Options are literally limitless. The best would be an Institutional LMS with tech support. If it is not available then depending upon the activity being planned following can be used
For live lectures ( Zoom and Google Meet)
Online Polls and Interaction ( Kahoot and Polls Everywhere)
Student Assignment and sharing resources ( Google Classroom)
Encouraging Student engagement and Q&A session ( Padlet)
Much of medical education has shifted online in recent years anyway. Classes at many universities are recorded for asynchronous viewing, UWorld, Pathoma, Sketchy, etc. The current crisis only highlights this even more.
Effective? I barely know what the topics are about! And the thing is that we can not easily assess foreign websites to improve our understanding! It has been so hard for us all in iran :)