Here's how you could do it for 30 degree isometric:

Make a precomp that is a square, about 1.5 times the longer dimension of your final comp. Put your isometric elements inside the precomp and scale each of your original elements to 173,2% (square root of 3 times 100%) on the y axis, then rotate them 45%.

In your main comp, add two separate Transform effects to your precomp, the first one to rotate the comp -45 degrees, the second one to scale the height to 57,7% (1 divided by square root of 3 times 100%).

Now you can drag anything inside the precomp x and y axis and it will become the 30/150 degree isometric axis in main comp.