This is a really important topic. Implementing these new tax rules correctly can be complicated.
As for the choice to have the same end-consumer price for all countries, this may work well for you if you sell products with high margins. Otherwise for example if you are based in Germany (19% VAT) and send an order to Sweden (25% VAT) the 6% difference can wipe out your profit.
The other option, the way the EU suggests to do it in this new regulation, is to work with a base price excl. VAT and then calculate the end price including VAT, based on the VAT rate of country of delivery. If a customer is not logged in -which is the case with most new customers) how do we know what end-price to display? Should we implement a pop-over on the landing page where the customer must choose a shipping destination? And how do we redirect him from there?
Or display the prices including the VAT of the country of the shop, then at checkout, after the customer selects the country to ship, recalculate the correct price. Who's gonna explain the Swedish costumer that the price he saw when he put the item in his cart (for example EUR 119) suddenly has changed to EUR 125 at checkout?
Can the Prestashop team to come up in time with updated code and a hand-on tutorial?