If I do the stage depths Combo do I sac both or just stage
Gonna assume you mean {Thespian's Stage}, {Dark Depths}.
Linking cards is always good.
Since Depths is legendary, you'll have to sac one of them immediately. I'd suggest saccing the real dark depths. Then you sac the stage for a token. Basically, you lose both but get a 20/20.
Sac the one with all the counters on it. You'll need the one without counters to get your 20/20.