Lag bolt vs structural screw (and length) for TV mount
1/4 lags should be fine even in redwood, many homes were built with redwood in the north Bay Area. Redwood is soft and has a lower withdraw force, I have 4 ea 1/4 x 3 lags holding a 78” flat screen I would use the same in redwood. 

I would use lags over structural screws for the higher shear force. No brand preference, just plain old steel, bright or hot dipped it makes no real difference if they are not visible.