Difference between /system/build.prop properties and setprop persist.adb.tcp.port (example) properties? What is the difference between properties manipulated in /system/build.prop file and properties manipulated by setprop, for example setprop persist.adb.tcp.port? Where is the latter property stored? Is there another properties file somewhere?
To answer your 2 last questions, according to several sources (1, 2, 3), thoses are stored in /data/property/. I couldn't find an offical reference about this location though.

For you, that would be in /data/property/persist.adb.tcp.port.