Legality of tip pooling in restaurants?

Hello great lawyers of Reddit! I’ve been trying to do my own research on the topic of “tip pooling “ unfortunately I’m finding it difficult to completely grasp. As far as I can understand, a restaurant can allow tip pooling but can’t have a hand in how it’s done? Example: if 2 servers decide they just want to split tips for the day, they are allowed to, but would have to split the tips by using Zelle or another app?

Server 1 makes 120$ in charge tips, server 2 makes 80$ in charge tips. Server 1 would have to use cash or an app to send server 2 the 20$ difference, rather than dictating how the tips should be split when entering into payroll?

I hope I’m explaining my confusion correctly and I’m very open to giving more specific examples if needed. I’m looking for specific laws or arguments for specifics on how tip pooling is to be legally correct.