By the time that the Titans "Doom Patrol" episode aired, actors Matt Bomer and Brendan Frasier had dubbed their performances over those of actors Dwain Murphy (Negative Man) and Jake Michaels (Robotman) respectively, so the only actor not shared between the Titans episode and the Doom Patrol series is Bruno Bichir.
The most significant difference between the Doom Patrol team that appeared in Titans and the Doom Patrol team that appears in the Doom Patrol series is that, in the latter, the characters have zero connection to or history with Gar Logan/Beast Boy (a fact publicly confirmed by April Bowlby).