Plenty of measurements - the most accurate being record profits while people worked remotely. Cleaner air, rivers and streets are also well known to have happened while people worked remote. Basically, other than rents going down and restaurants and shops closing there is little data on why remote work would be negative.

for WFH you have to be disciplined or, yeah, you end up with Work-Life Integration. I won't go into specific techniques or ideas but you have to be very disciplined with yourself when working from home. If you're not then you either start slacking off and eventually get fired or work just becomes all consuming 24x7 and you have a worse work-life balance than when on-prem.