By default, page load rules in DTM load at the bottom of the page. This setup works for most scenarios, however there are circumstances where it wouldn't be as effective. Consider the following:
- If the rule is dependent on in page content, such as a data element loading, then loading on DOM ready could be more effective.
- If there are rules in the property that rely on the outcome of a specific rule, loading that rule at Top of Page or Onload would ensure that it fires first.
For deeper look at how this works, check out the documentation here: https://marketing.adobe.com/resources/help/en_US/dtm/load_order.html