We suggest you keep the talks live and maybe leave recordings online for a short period of time after the conference instead of using recordings, because this is also one of the aspects which bring virtual and in-person conference close together. To make successful live online talks, you will need some training with your speakers, so that they are familiar with the setup. We have used Zoom for this and even first-time users did not have any problems.
Poster sessions can be realised in different ways. We used a dedicated forum on our webpage to upload the posters and gave other participants the chance to comment and ask questions. Additionally, each poster presenter had 3 minutes to talk about their research. One other option is to use Twitter as the RSCPoster Twitter conference has shown with a huge success.
We are still experimenting ourselves to find the right format for networking and this is an open question which will be answered when more virtual conferences become available. In the end, we want to leave you with a word of encouragement: VIRTUAL CONFERENCE? SUDDENLY? YOU CAN DO IT!!!