Surge protection you can put a MOV in after the fuse for peace of mind but transients get limited by core saturation.
Except for for fast transients which can be coupled through the inter-winding capacitance bypassing the magnetic circuit altogether.
Some X and Y capacitors on the mains input can help with knocking back those fast transients before they get coupled through. In that case I like to include a MOV on the primary circuit, more to provide protection for the X capacitor than the rest of the circuitry.
These are split-bobbin semi-toroidal construction, primary and secondary are apart giving very low inter-winding capacitance and 1,500VRMS rated hipot.
I say (differential) fast transient won't make it far enough and core saturation and impedance will be a good enough filter.
For common-mode transients, a MOV/X-cap is of no use. It can help with back-EMF is there if a relay or small switch.
For many years I used to design using a fuse, MOV, then power transformer.
Fuse is sized typically 167%-300% of max. primary current, depending on the safety standard. MDL-1/4A is 3.2Ω (and $10 ea. now?) so the MOV would get an easy life.
130VRMS MOV (clamp max. 340V). This works fine but I realize the MOV voltage rating is tight, too low for nowadays. Mains voltages are higher and MOV aging- although I have not seen a problem, I have several used 30 year old 20mm 130VRMS MOV's and I checked they are 50uA at 122VRMS. Today I would use a 150VRMS part for 120VAC mains.
But even using a MOV you still only have it down to ~2-3x mains for transients. But I think the transformer magnetics clamp it. So I don't use a MOV anymore.
OP be careful with running traces underneath the transformer, I find you can get induced hum (right hand rule), and keep primary clearances in mind.