Max BR1 Pro 5g WiFi lan external antenna metal van

Would a reasonable setup on the BR1 5g with external antenna to connect from inside the van be to use the 5g wifi internal antenna for lan use leaving the 2g WiFi for external antenna wan connect? Or just get another cheap router and plug in into the BR1?

So after finding more info in the forum I see the unit has both radio frequencies on both WiFi antenna inputs, and is wan/lan. So is the preferred setup to run a separate AP WiFi for lan because of performance issues of utilizing the BR1 in simultaneous WiFi lan/wan mode?