It's not stupid. The answer is in the running. Where does it slow down? That's where it needs it. The length willl vary on your track condition. I have 4 on a double loop in a 7 by 7 area. This is using the same transformer. If you block it, you separate your feed/power anyway. Rule of thumb, one every 4 to 8 feet. O Track is equivalent to 16 gage wire(info from CTT), That is the reason they make a 3 ft straight, less connections less resistance and less bumps!!!
In O scale the track being 16 gage the experts like 14 gage feeds for the permanent layouts. I'm using speaker wire. HO? I don't know, around 18 gage at least. I have to research more. I use 22 gage a lot for wiring. I don't have a reference to answer this now. Naturally, the larger wire, the safer it is.