Filling a flight plan does help controllers, so something is in the system.  If you are flying around doing instrument work with a local approach control, they do not enter a flight plan for you.  They put you on a local squawk code.  Those flights will never show up in flightaware.  Even if you go to an airport that is within the approach controls airspace, they will sometimes not put an external code in for you.

If you file your flight plans online you can file a VFR flight plan and that will be put it into the system.  When you call up ATC, they will depart that flight plan, but not the VFR flight plan it selft.  That sounds confusing, but what it means is that flight service is responsible for tracking VFR flight plans.  The enroute centers and approach controls are responsible for IFR flight plans. If you want to activate the VFR flight plan, it always has to be done with flight service.  So by filling a VFR flight plan online, and the controller departing the flight plan, you do not have to deal with flight service at all and they will not be looking for you, because the "VFR" portion of the flight plan was never activated with flight service.  When ATC terminates you at your destination, the flight plan is removed from the system.

The only trick with filling IFR flight plans and then converting them to VFR "flight following" is if you are departing from a towered airport with an IFR on file.  The tower still has get a release from the approach control to let you depart VFR.  That could lead to a delay at busier airports.

Luke Alcorn
NATCA ZJX Safety Rep