Read each individual attribute for the rules on whether it should be placed on hierarchies or signals.
In general, when an attribute is placed on a hierarchy, it affects only that boundary, and not the items inside that hierarchy. For example, placing a DONT_TOUCH on a specific level affects that level only, and not the signals inside that level.
There are some exceptions to this rule. These are DSP_FOLDING, RAM_STYLE, ROM_STYLE, SHREG_EXTRACT, and USE_DSP. When these attributes are placed on a hierarchy, they also affect the signals inside that hierarchy.