Difference Between Title Block and Border File

Traditionally for may firms the Title Block & Border file are the same. The information that is unique to the drawing/sheet is placed in the sheet. i.e Sheet number, revisions dates, etc.

There are certainly other ways to do this. All have their pro's and con's which will vary depending on the size and type of project.

If you have different border formats you could reuse the same title-block. If you ever have to change something that's supposed to remain fixed (logo, address, ...) you could just change the one title-block and have that change propagate to the other formats automatically through References. There is nothing fundamentally wrong with your approach.
You certainly don't need separate border files, separate models within one file could work as well.
As long as at least the variable part of the title-block is placed on the Sheet itself there should be no real problem. One consideration in how you set it up is what you'd like to see happen to your drawings, if ever the "fixed" part of your title-block needs to be changed.