Many of the millerites didnt beleive the trinity doctrine because many had come from the christian connection a non trinitiarian group. As a result the SDA still have many in there church who dont beleive the trinity. Of course the official position in the SDAs is the doctrine of the trinity.
The JWs also had connection with the millerites and the second adventists which influenced there position against the doctrine.
In practice christians worship Jesus and the holy spirit and Jehovah without thinking of the workings of the trinity doctrine .