G'day Mate,
Symptoms of Nose heavy = In no special order, nose drops a lot when throttle reduced for landing, & elevators are rather sluggish, when plane rolled inverted large amounts of down elevator are required to maintain level flight, nose drops a lot in fairly gentle turns, right or left. There are more but that will do to be going on with.
Symptoms of tail heavy = In no special order, elevators are super sensitive, plane is hard to land because of elevator sensitivity, & tends to come in to land with tail low, when rolled inverted, plane climbs with no elevator input, & so on, you get the idea. Not the ideal setup, but as was stated earlier, when the sweet spot is found, most planes are improved dramatically.
So don't be afraid to move your balance point, to find the sweet spot, just do it small amounts at a time.
The CG location shown on most plans & ARF instruction sheets, are only a starting point, for the first few flights, it is up to you to adjust or trim the plane , until you are happy with the way it flys.