I've always found it helpful to be able to drag new guides from the rulers while the Transform function is active on a layer/object. This was particularly helpful for object such as logos that have built-in white space. If I try to create guides before transforming, the guides only snap to and center based on the drawn pixels. If I do Edit > Transform, then the object's full artboard size is shown and allows for better centering and edges for snapping ruler guides to. This was always available until the recent Photoshop CC 2019 release.