Trying to Squeeze a Bit More Speed from LBR20

I am looking into adding the 4 MIMO antenna scheme into my Orbi LBR20.
Thinking of using Wilson Yagi antennas for the primary, and just paddle antennas for the secondary.
Has anyone tried this?
Also, just as a general question (sorry if it's been asked a million times), what is the difference between the primary & secondary antennas?
Any other ideas in getting the most out of the LBR20, which seems to be effected by congestion A LOT!!