Europe is a huge, close-together market — and a patchwork of currencies and tax rules. The stores that expand smoothly are the ones whose platform handles the complexity for them.
Show local prices
Shoppers convert better in their own currency. That means presenting prices with reliable rates and snapshotting the rate used on each order, so totals never drift.
Get VAT right
VAT is charged by the customer's country for most consumer sales. The One-Stop-Shop lets you report it all through a single return instead of registering everywhere.
Make it structural
Retrofitting this with plugins is where the headaches come from. When currency and tax are part of the core, a new market is a setting — see International. This isn't tax advice; confirm your obligations with an adviser.