I think the most important thing is to have the CG in the right place. It affects the way the plane reacts to all the other settings, geometry, etc.

Pretty much everyone already knows and is scared of having the CG too far back.

However, many make the mistake of having too much of a "good" thing and move the CG way forward. That makes takeoff much more difficult, especially when you don't necessarily know how much elevator travel is enough. You can end up pulling elevator on the takeoff roll, and having the plane leap into the air once the elevator power overcomes the nose weight. I've even seen planes do that, and people assume it is tailheavy because of the "pitch-up".

Then it will be hard to land as well, as there will be even less elevator power available due to lack of propwash. I have had a friend lose a plane on the first flight because the plane was too nose haevy and he could not get the nose up to make it over the trees at the approach end. Not big trees, just the ones at the end of the runway.

The CG ought to be 10% of the MAC in front of the neutral point of the plane for the first flight. I calculate the neutral point then use the above "rule of thumb". This has always worked very well for me. I then move the CG back to 5% or less depending on the type of plane. Of course, calculating the neutral point is the fun part. I can help you with that if you want.