You've got this right. FAS-DPD has more accuracy, resolution and range compared to DPD. With FAS-DPD, you can get a resolution and accuracy of 0.2 ppm if you use a 25 ml sample size or a resolution and accuracy of 0.5 ppm when using a 10 ml sample size by "counting the drops" until the sample turns clear and one can measure up to 50 ppm if one adds more initial powder when they see a pink flash when adding it (i.e. if it does not stay pink/red).
With DPD, it starts to bleach out above 5 ppm, pretty much is completely bleached out above 10 ppm, and is hard to get better than 0.5 to 1.0 ppm accuracy from the visual "compare the color" test (though measuring instruments can do better).
OTO only tests for TC, but it doesn't bleach out so is a very definitive test of whether you actually have chlorine, even at high levels.
The above is why we recommend FAS-DPD chlorine tests, though having OTO as a backup for very high chlorine levels (just to be sure there is chlorine) can be useful.
Once one gets to know one's pool and has a fairly regular and stable chlorine demand, then one can use a less accurate chlorine test on a regular basis, but should probably double check with FAS-DPD at least once a week. That would save on reagents.