I see. So they really aren't connect like Buffy and Angel were?
Not like
Buffy and
Angel were when they were both on the WB and had regular crossovers, but kind of like they were after
Buffy moved to UPN, the crossovers became much rarer, and the shows diverged stylistically even more than they already had. They're in the same universe, there are occasional connections or Easter eggs that you catch if you watch both shows, but you can follow either one as a complete story by itself. The two were designed to stand separately since they were aimed at such different audiences.
Actually the modern
Who universe has three series aimed at three different demographics:
Doctor Who for families,
Torchwood for adults only, and
The Sarah Jane Adventures (now sadly defunct due to its lead actress's death) for younger viewers. Although there's a lot more distance between TW and DW than between DW and TSJA. Each show crossed over into DW (and the Doctor appeared twice in TSJA), but you'd never see TW and TSJA overlapping with each other, because there's just too great a stylistic mismatch there.
(There's also the unofficial Australian spinoff
K9, which can exist because freelance TV writers in England retain ownership of the characters they create and can use them elsewhere as long as they don't reference anything from
Doctor Who overtly. It's kid-oriented like TSJA, but nowhere near as good.)
So Torchwood is to nuBSG like nuDW is to TNG?
Stylistically? Kind of, except TW goes farther with the profanity and nudity than BSG was able to do on television, since the broadcast standards in the UK are different. Maybe more like
Game of Thrones, although I've never seen that.
Just wondering, does the Doctor ever appear on TW?
One part of him did, but was never identified as such.