Hi
1) Sure - you can have as many curves as you want in a roast, and log temps or control values to each independently. In each of your P1-P5 profiles, you could create a new Curve Template. Name it, and set it to a reading curve. Then, whenever you tag a profile in a roast, you'd automatically get a new blank reading curve in the roast for recording data. SO, you'd have two in each roast–the control curve Roastmaster gives you by default representing the Behmor heat, and then the new reading curve courtesy of the new Curve Template. Just tap the graph to select the curve you want to edit, and then tap the digital readout to enter a temp.
2) I'm not quite sure I follow, but the only thing that Data Logging "unlocks" is the ability to link to a wireless probe. Otherwise the app function is identical with or without it. In other words, you can record as much data as you want to as many curves as you want either way. The Data Logging option just does it automatically. You wouldn't need the Data Logging option unless you reached a point where you were tired of entering manual temperatures.
Let me know if I'm not understanding.