The number of tracks depends on the RR and how busy and location as mentioned above. A example is the the East Broad Top in Pennsylvania. I think they orginally had an 8 stall roundhouse at their HQ at Rockhill Furnace (Orbisonia) PA. They kept and serviced 6 steam engines there in modern times. All 6 are still there and there is a gas-electric in a 7th stall. They ran 4-8 trains a day I think in the 40s and 50s.
The PRR had 2 roundhouses and TTs in Conway near where I grew up and had many tracks on each. They serviced a 4 track mainline with many trains a day.
Some short lines only had 1 or 2 locos and used an engine house that looked like a garage - and had 2 or may 3 tracks off the table plus the lead.
And the smallest extreme is a TT at the end of a branch with only 1 track - the lead. It would be used to turn the loco that came to the end of the branch.
Most major mainline terminals however had many tracks.