If you’re going to use a barrier, landscape fabric allows air and water to be available to the roots. Plastic does not, and if there are not enough holes punched, the accumulating water can carry the much away.
Roots naturally grow at their preferred depth in the soil and putting too thick a layer can cause them to grow up into the mulch, where they are much more susceptible to drying out and being exposed by erosion or decomposition. I try to maintain two to three inches, no deeper, and not to the trunk as it can cause rot by holding moisture against it. It can also create shelter for pests to eat the bark undetected until it’s too late.
In a zone with cold winters, it’s a good idea to mulch after the ground freezes rather than right before. The goal is not to keep the soil warm, but to maintain a consistent temperature. Alternate freezing and thawing is a problem for several reasons.
If fresh wood chips are used, a cheap nitrogen fertilizer should be added to the root area of desirable plants to replace the nitrogen depleted by the decomposing process.