I think the idea of drawing the load line is to estimate the optimum load to achieve (for example) maximum efficiency while keeping the output linear in a power amplifier.
In my opinion the load line is not changing depending on your output.
Which do you mean EDA Tool Play or Actual Measuremnt ?
If you mean EDA Tool Play, do DC Analysis with sweeping Vdd.
Then plot Idrain with x-axis as Vds or Vdrain.
What voltage is used as x-axis depends on circuit.