You can add an if statement to the formula to only add the double-space if the Type’s Prefix field isn’t empty:
[Step 1 Page].Type.Prefix + If(IsEmpty([Step 1 Page].Type.Prefix), "", " ") + ReplaceRegex([Step 1 Page].Name, "^.* ", "")
(I think discourse is converting the double-spaces into single spaces in the above formula)