Can anyone link the sources for Biden taping in a set of the fake Oval Office from ~2021?

They were available. Held in what was reported as inhumane conditions by Biden (an early loss to his popularity, while fortifying support for those who knew it was stolen)

Safety measure to ensure the plan went uninterrupted with no downside?

That was a perfect normie speech (where Trump requested the media and said it would be one of the most significant days of USA history) - outlining undisputable facts of Trump's 2016 presidency with a calm presentation, while showing Trump's loyalty and respect to the country. Drawing attention to all of the Dems and Biden's failures. I expect him to be nominated shortly after this for SOTH. What a coincidence GOP just secured the house? Stay strong...