Only problem is that there are no traffic lights in air, fly safe best is to fly at different heights with reference to the same ground level and sequence your landings properly.
Sometimes another P3 will interfere with the video transmission. Other than that, the RC is 2.4 Ghz spread spectrum frequency hopping technology, allowing multiple aircraft flying at once.
If you stand close together you may well experience some interference - as shown by interference on your FPV feed. Don't believe that there are any control issues.
We have had 5 P2 /P3s together for the clip below and I was once out with 10/11 other units, P2/P3/I1/F550 - lots of interference but we were all standing beside each other.