I think Koenig did a good job as Bester in B5.
That's where I think actors fear of "role identification" is BS. He was a great villain as the representative of Psycorps in B-5. I never saw him as Chekov in at any time in B-5. It's all the actor and the role.
Of course I did like him on the show Viva Variety where they had him do a sketch called "Checkov Does Chekhov." He was dressed in old Russian period clothes and started doing "Uncle Vanya" when their character Johnny Blue Jeans ( Michael Ian Black ) came out wearing a really lame space costume. They gave their apologies and Koenig continued with the play. Then the play turned to what I think was one of the best lines ever on TV as the female host, Mrs. Laupin ( Kerri Kenney ) shouted "lookout Uncle Vanya, a Klingon!" So of course Uncle Vanya had to fight it.