Traffic light KPI with an threshold input

You only will need a disconnected table if you want to have single measure for the condittional formatting.

What I mean is that assume you want to have this measure:

Condittional formatting =
SWITCH (
    TRUE ();
    SUM ( Table[ABC] ) < 1000; "Red";
    SUM ( Table[ABC] ) >= 1000
        && SUM ( Table[ABC] ) >= 2000; "Yellow";
    SUM ( Table[ABC] ) < 2000; "Green";
   SUM ( Table[ZYX] ) < 1000; "Red";
    SUM ( Table[ZYX] ) >= 1000
        && SUM ( Table[ZYX] ) >= 2000; "Yellow";
    SUM ( Table[ZYX] ) < 2000; "Green"

)

If you use the same table to get the values since you have column ABC and columnZYX in the same table the calculations are picking up the first  column you place on the switch measure in this case column ABC so the result would be to have a line with all values equal. In this case you would need to have the disconnected table making the specification that calculations for column ABC would only pick up the column ABC.