Yes you are on the right track, but ActiveX controls are not ideal for use in Word documents.
You need a range target for the text. It could be a table cell, a paragraph, a bookmark, a content control, a variables (and use a DocVariable field), etc.
Here I have created a bookmark "bmText" to serve as the target range.
Code:
Option Explicit
Dim oBM As Bookmark
Dim oRng As Range
Private Sub OptionButton111_Click()
If Me.OptionButton111.Value = True Then
Set oRng = ActiveDocument.Bookmarks("bmText").Range
oRng.Text = "User will email form"
ActiveDocument.Bookmarks.Add "bmText", oRng
End If
End Sub
Private Sub OptionButton211_Click()
If Me.OptionButton211.Value = True Then
Set oRng = ActiveDocument.Bookmarks("bmText").Range
oRng.Text = "User will mail form via FedEx"
ActiveDocument.Bookmarks.Add "bmText", oRng
End If
End Sub