For all ProtonVPN clients, there should be a toggle option in Settings that allows you to exclude Smart Routing servers from your connection. Something like:

"Exclude Smart Routing servers (use only servers physically located in your selected country)"

When you set up your Default Connection to be in your own country, you may be connected to Smart Routing servers which are physically located in another one and therefore will have worse latency.

For example:

A user in Argentina sets their Default Connection to "Argentina" for minimal latency. Without excluding Smart Routing servers, they might connect to a server physically in United States, increasing latency and worsening the experience.

This could be added in Settings -> Connection -> Advanced Settings and would help a lot users that want the lowest possible latency while protecting their privacy.