The Τracker4 is a full featured TNC and can handle beacons itself when you give it locations via GPS. The Mobilinkd devices are simply modems just connecting the radio to the software. They can't do much without client software.
When you run APRSdroid it's capable of picking up location from the phone's GPS. The default configuration will attempt to do posit beacons on some schedule, I think using Smart Beaconing. Which the Tracker is probably also configured to do. So you're double tapping and probably sending a lot of position out.
I have my Tracker3 set to Smart Beaconing with a dedicated GPS for it. So it runs regardless if I have APRSdroid connected or not. When I use APRSdroid I have it send a position packet every 30 minutes on a fixed interval. This packet contains the voice frequency I'm using and is simply informational for any other stations in the area. APRSdroid is also the only way to do messages in my APRS station. The Tracker/data radio don't really have any ability to easily include voice information but it does positions without any intervention when the truck is running.
I use OpenAndroidMaps with my APRSdroid offline. It's relies on Mapsforge V3 so it's very long out of date. Mapsforge is up to V5 and even that has I think gone stale for a while. But it works and if you download them while they are still available it'll be fine for a while (the V3 from OpenAndroidMaps were last updated late 2019, early 2020 but that will be the last update they run). The monster KS9N whole country map is what people used to use but it lacked quite a bit of detail is now really out of date by several years.
www.openandromaps.org