My guess would be that when you first turn on the smoke it draws more than usual to get it warmed up but then drops down a bit once going. I don't have legacy so I have no idea how that works.
One question which may sound silly but I will ask it. With the smoke off do you notice much fluctuation in the amp draw as the engine runs around the track ? I have about the same setup as you and I run TMCC and DCS. I normally see some fluctuation in amp draw but it is because of track that might need cleaning. When I really clean the track well, the fluctuation all but stops except for 1 curve where is adds resistance to the loco.
Could it be that when adding the smoke unit into the mix the amp draw is a fair amount higher and you notice the fluctuation more.
Ed
