"Toilet bowl" in GPS flight is usually caused by bad wiring (must neatly and tightly twist all high current wire sets) or by bad mag calibration.
I understand that mag calibration can really only be done with telemetry, that USB cable causes mag issues. I have heard one person say that they were able to do a usable calibration with a USB cable though.
LP hasn't released yet (planned for September).
GPS modes require GCS -> Attitude -> Settings -> Attitude Estimation Algorithm = GPS Navigation (INS13)
The GPS mode you want to play with first is called VelocityRoam. It is like PositionHold if you leave the sticks in the center, but it moves as expected when you move the sticks. If you hold left bank stick, it moves left as long as you hold the stick. Beware that the motors stop if you go to lowest throttle stick.
The other GPS mode I use is PathPlanner (warning!!! advanced!!!) where you set up waypoints. Only do this after you successfully fly VelocityRoam (or PositionHold). You create a plan by clicking on the map and then pressing Control-a to add a waypoint. Make the first one close by so you can watch closely. Do this several times to make a flight plan. Drag the waypoints around with the mouse if wanted. Right click and use the flight plan editor. You must set the aLtitude and velocity for each leg (they are 0 otherwise). ALtitude should be at least 4 (meters, above HomeLocation) for safe testing. Then upload the plan to the FC. You need a big, open field for first tests. You must have an accurate (especially aLtitude), close by, HomeLocation stored. ALtitude is critical. It will fly at that aLtitude plus the 4 that you put in the flight plan. Take off and hover fairly close to first waypoint. Switch to VelocityRoam for a quick test, then switch to PathPlanner mode and watch it very carefully and be ready to switch back to another mode IMMEDIATELY. It will loop the flight plan over and over till the battery runs out, so you must switch back to another mode and land it when you want to.
If you use a laptop at the flying field, but don't have internet access there, then at home you need to right click the map and do "Rip Map" for your flight area to store the map on the hard drive. I added all my normal flying sites this way, but only about 300m x 300m for each one or else it takes forever to download. I actually do a larger area at lower resolution too.
I recommend that you have at least a 3 position flight mode switch (you can very carefully use failsafe mode to make another flight mode and switch the transmitter off for the 3rd position). You need to take off without GPS and be able to disable GPS in case of a fly away, so use your favorite non-GPS mode for that. An auto-leveling mode is highly recommended even if you think you want to use Rate, don;t use Rate. You need to it to auto-level if you have lost visual orientation and it is a long way away... You need to be able to test it in GPS mode without PathPlanner and also stop it wherever it is if you don't like the path plan, so you need VelocityRoam. Finally you need PathPlanner mode to actually fly the flight plan.