Actually when we fulfill shopify orders for clients in the EU or Canada we declare less than 20 USD in the ePacket package, however, not every supplier will bear it in mind. So there are two suggestions for you.
The first one is to make note the customs tax policy and some terms in the foot as well as FAQ area, so that clients visit your store could know them once they paid attention.
The second one is to confirm with your supplier or order fulfillment agent about the package value to each country in the EU, make sure not exceed that value.
Via the two ways you can lower down the dispute rates caused by the custom tax. Of course, you can also offer some coupons once some clients complaint about the packages tax they paid, explain a little bit about the country customs policy and offer a coupon would be better for customer experience.