The involved discussion on TMP caught me by surprise, so I looked at my sources. Sure enough, Zweguintzow says both Infantry and Cavalry generals wore the white plume (with black and orange feathers at the base) with the common uniform. This has influenced a number of secondary works. Zwenguintzow’s source is unclear as Viskovatov implies the Infantry generals used (all) black plumes. Leonov, Popov, & Kibovsky show the all black plume.
(Don’t forget the dark green plume of Jaeger officers 😉 )
In my opinion, it’s pretty certain – only cavalry white. I think this is a goof by Z. But I’ve learned for a while now that what I know may change tomorrow, so I try not to state things imperiously.