pros and cons of submitting a conference paper in first round vs second round I am not very familiar with the pros and cons of submitting a conference paper in the first round vs second round. In particular I am referring to the dates given for FG 2021 here -  http://iab-rubric.org/fg2021/important_dates.html.
I would prefer to submit in the second round as it gives me more time. However, is there a chance that there would be no second round if sufficient papers have been accepted in the first round? Could someone briefly explain to me the first round and second round process. Thank you!
The conference's important dates precisely mention both dates, namely the first and the second submission rounds. Although I understand your worries, I do not explicitly see on the CfP that the two overlap.
So I would suggest you to move as you planned. But! In any case, since those sensitive matters are not well defined, you can easily send an e-mail to the respective organizing committee/program chairs with your question. Thats what I would do if I were you.