RFK draw from both about equally.
All the more important to make sure Jill Stein and Cornell West are on the ballot in all 50 states - almost all of their votes would be drawn from Biden.
This is also my thinking. RFK Jr draws about equally from both sides, except in Dearbornistan and other Muslim places, where he draws more from Biden than from Trump. BUT, the greenie and the gonie (Stein and Cornel West), draw mostly from Biden.