In your Revit model, the level is the key starting point. Everything, ultimately, relies on the level.
Floor plans and RCPs are directly associated with a specific level. You cannot have a plan without a level. And once a plan is tied to a level, it cannot be associated with any other level.
This tight integration between level and view also can cause the NAMES to be tightly integrated. By default, the name of the plan or RCP view for a level is the same as the actual level name. Renaming one can change the other. And this is precisely where you need to pay attention.
We all have gotten somewhat lax about reading the warnings that any software pops up, usually clicking YES or OK without thinking. In Revit, we need to read the pop ups. It is trying to tell us something and quite often, it is trying to tell us something important.
When you rename a level, Revit will ask you if you want to rename the associated views. Likewise, when you rename a plan/RCP view, Revit will ask you if you want to rename the level. There is no set rule about clicking yes or no, the only rule is that you need to read what Revit is going to do and figure it out.
Example 1: you start a new model, and you rename the default “Level 1” to “FIRST FLOOR”. Revit asks if you want to rename the associated views. Well, yeah, you probably do. It wouldn’t make sense for you to have your level be “FIRST FLOOR” but the associated plans be “Level 1”. So let Revit rename away.
Example 2: you have a model that you have been working on and you create a new floor plan to show the existing phase of FIRST FLOOR. You go to rename the view to “EXISTING FIRST FLOOR” and Revit asks you if you want to rename the level. In this case, no, because it would change the level name from “FIRST FLOOR” to “EXISTING FIRST FLOOR”, which in this model makes no sense for the levels.
So, the big rule is to read what Revit is telling you, and make a proper decision from that.