Does it make sense for Text-type data items to have both a Related Table and a Lookup Name defined? Shouldn’t it only be one or the other? What if there is an existing data item that already has this configured — is there any server impact to how either behave?
It doesn’t make sense for a Text-type data item to have both a related table and a Lookup Name configured. If both are set, the data item will behave as either a table lookup or a list lookup—but not both. There is likely an order of precedence that determines which behavior takes effect. Based off of initial investigations, it looks like Table Lookups would take the precedent. To check, open the app the data item is used in and see what field type is being displayed. That would be the precedent.
If you encounter a data item with both fields populated, it’s recommended to remove or adjust one of them, as having both is considered an invalid setup.