They employed some of the same people, though relatively few. The Okhrana headquarters were sacked and burned, Okhrana agents were subject to automatic arrest, and its leadership executed. As for tactics, that's inevitable with any secret police organisation: but there's less in common between the Okhrana and the Cheka than there was between the Okhrana and, say, most other European secret polices.
As for takeover of one of the "largest leftist groups" in Russia-- are you referring to the SR Combat Organisation?
No, I'm not, that's a ludicrous simplification. As I said, most political repression in late Imperial Russia was handled by the military and regular police. It was still huge in scale.