Low Priority vs High Priority AB tests

If you have the fine grain priority setting turned on from Admin, then activity with the highest number takes precedence. So, if multiple activities are assigned to the same location with the same audience, the activity with 999 takes precedence over the one set to 0. 

If you don't have fine grain set, you will see low, medium or high.  Low priority will essentially be 0 and occur after high. 

https://experienceleague.adobe.com/en/docs/target/using/activities/activity-settings

Low-priority A/B tests typically focus on minor changes with less potential impact, such as adjusting colors or wording. They require fewer resources and are less critical to overall business goals. High-priority A/B tests, on the other hand, target significant elements like the McDonald's menu, pricing strategies, or checkout processes, where outcomes can directly influence revenue and customer experience. Prioritizing A/B tests helps allocate resources effectively, ensuring that efforts are concentrated on changes that will most likely yield substantial results.