is SF4Cl2 polar, nonpolar, or does it depend on the arrangement of atoms?

The S is in the center and the 4 F and 2 Cl atoms will bind to the S forming an octahedral structure. That means 4 ligands will be bound to S in one plane and the other 2 sticking out of the plane in two opposite directions. If the arrangement is symmetrical, the molecule is nonpolar, but if it is asymmetric, the different electronegativity of F and Cl will induce a polarity in the molecule.

PS cis and trans refers to direction of the so called ligands (groups attached), if the y are both in the same side its cis, if on opposite sides is trans. Like this:

f cl

cl f

trans

depends on the arrangement of the atoms.

if the Chlorines are opposite to each other, their charges will cancel out, and the molecule will be nonpolar.

But if a Chl orine faces a Fluorine, then their will be a net charge in one direction, and molecule will be polar.

If the Cl atoms are trans, then it is non-polar. If cis, polar.