The rule of "hours of exposure x number of people x closed environment = +/- risk" applies. Or to put it another way: The more people I interact with, the longer that interaction, the more closed the environment, the higher the risk of COVID-19 spread.
I haven't read any science that contradicts that basic, simplistic formula. It's easy to extrapolate from. Gathering 30 people in a park over a leisurely, 5 hour afternoon get together to celebrate a birthday = less risk than gathering 10 people for 2 hours in your living room for that same celebration.
Moving, fresh air is better than still air or recirculated air. An outdoor environment greatly dilutes the virus aerosols, allows them to spread and move and dissipate far more easily than when those same aerosols are trapped in a room, so there's far less chance for you to inhale ENOUGH of those particles to create the viral load necessary in your system to infect you.
It's anomalous to putting one drop of blue dye into 8 oz of water vs that same one drop into a 20-gallon tank. The 8 oz will turn blue. But you'll hardly notice a color change in the tank. (Disclaimer; those portions may not be an accurate representation, I'm just trying to make a point)