Flat vs Standard Rate Vat

I have only been selling on Amazon for a few months now with €4000 in sales. My business is registered in the Uk but I am based in Ireland. Since I don’t have a physical address over there I am termed an NETB (Non Established Taxable Person) This means I have to registered for Vat.

My question is: which is more suitable when selling on Amazon; Flat rate 7.5% vs Standard Rate.

Considerations: Flat rate margins are 5-20% vs Standard rate profit margins 20-40% (same products) Plus I can claim back standard rate on expenses and Amazon fees.

Flat rate: Is more profitable plus its easier accountancy wise. However, profit margins are far better on Standard rate so profit seem higher on standard rate.

Any input would be great guys