And you will continue to see TP. The waste tanks in an RV are HOLDING tanks, not septic systems, and while some toilet paper in the black tank may dissolve somewhat if you leave it in there for a while, the tanks are designed just to hold the waste until you can dump them into a proper sewage system.
Most of us don't use ANY treatment packages, just plenty of water.
Empty the gray tank whenever you want, though it may be best to get it over half full, but for the black tank it's best to wait until you are over half full, and 3/4 full is probably better. "How often" is, of course, dependent on how much use it gets, so empty whenever it gets near full. After dumping, put two or three gallons of water in the black tank to aid in keeping things moist for future use.
Original equipment tank sensors generally collect stuff from the contents to the point that they are unreliable as gauges, although some cleaning is possible to occasionally make them work right for a little while. Some add-on sensors, such as the See Level brand don't have that problem.