Looks like JTH7 is a manual-ignite torch, right? Like, you need a separate striker ... This one would be great for using propane (UNLIT) to search for vacuum leaks, more maneuverable than a small bottle with nozzle attached.
Exactly. You described the p/n JTH7 torch well, including the maneuverability and use for checking vacuum leaks or adjusting the idle mixture on your 70s-era carburetor.
The other torch shown, p/n BZ8250HT, has a "lock" feature on the "gas on/off - ignitor" clicker thingie, so one can lock it in the "on" state as desired. It too is maneuverable, and it could be "locked on" and
then gas applied (there's a valve on the tank fitting), so as to override the ignitor feature and behave much like the JTH7.
I like having them both, each has their place.
For the record, EACH has a valve mounted on the tank fitting (at the end of the hose) that's used to turn-off and otherwise control the volume of gas admitted to the torch handle. The valve is controlled by that black twist knob visible on the top of the fitting. Each also has a holder that clips on the small propane tank; the holder allows the tank to be carried on one's belt / waistband.