Try running them together but uncoupled. If they make about the same speed (which I would expect from the same manufacturer), go ahead and couple them. You may find it useful to connect them together with a wire between the pickups. It’s a real nuisance otherwise when the e-units get out of sync. You can make a connector just by putting a single connector pin on the (black) wire from each unit, one male, one female. Cover all but the business end of the male with (black) shrink tubing.
They are designed to be run together. There is a switch under the body to set for normal (single unit) front or rear when running two units together. This lights the correct lights for a two unit train.