This is not about WFH vs lunch conversations but about working in a quiet environment with minimal disruptions vs in a noisy open office with tonnes of disruptions. Good measures for you:

https://www.inc.com/geoffrey-james/science-just-proved-that-...

https://www.inc.com/jessica-stillman/new-harvard-study-you-o...

https://www.bisnow.com/london/news/office/the-proof-is-here-...

https://www.forbes.com/sites/billconerly/2018/08/16/open-off...

https://www.entrepreneur.com/article/313034

For the bonus:

Commuting is also pretty bad for productivity.

https://www.tlnt.com/how-commute-issues-can-dramatically-imp...

https://www.insperity.com/blog/commuter/