Draw has styles.
Create a new style (named ‘myTextBox’ e.g.) based on(inheriting from) Text/A4 (e.g.) with the settings you want.
For each page only containing TextBox shapes you may now use Ctrl+A to select all of them, and assign the new style by doubleclicking on its name in the Stylist (Sidebar / Style).
If you need to treat shapes of different shape type differently, I think you will need a lot of patience for the manual selection or a macro to distinguish the objects for you.
[Edit about 1h later]
If you know how to place a Basic module, and how to adapt the two hard coded strings “myTextBox” and “A” for optional parameters to your needs, you may use the following module to automate your job:
REM ***** BASIC *****
Sub applyShapeStyle(Optional pStyleN As String, Optional pShapeType, Optional pMode)
If IsMissing(pStyleN) Then pStyleN = "myTextBox"
If IsMissing(pShapeType) Then pShapeType = "com.sun.star.drawing.TextShape"
If IsMissing(pMode) Then pMode = "A"
doc = ThisComponent
cSel = doc.CurrentSelection
Select Case pMode
Case "A"
drawPages = doc.DrawPages
u = drawPages.Count - 1
For j = 0 To u
j_page = drawPages(j)
applyShapeStyleToCollection(pStyleN, pShapeType, j_page)
Next j
Case "P"
dp = cSel(0).Parent
applyShapeStyleToCollection(pStyleN, pShapeType, dp)
Case "S"
applyShapeStyleToCollection(pStyleN, pShapeType, cSel)
End Select
End Sub
Sub applyShapeStyleToCollection(pStyleN, pShapeType, pCollection)
nextStyle = ThisComponent.StyleFamilies.getByName("graphics").getByName(pStyleN)
u = pCollection.Count - 1
For j = 0 To u
j_sh = pCollection(j)
With j_sh
If .ShapeType = pShapeType Then .Style = nextStyle
End With
Next j
End Sub
[/Edit]