I have been using Mullvad since forever (actually recommended by the site of the article). They are extremely helpful, and are generally recommended in VPN reviews that do not have affiliates (including the site you linked to).

They do have both wireguard and openvpn options, as well as an app with a GUI (with support for both).

My favourite part is the support though. I got help with weird openvpn configs that didn't get answered in the openVPN forums for ages, within an hour.

I am a very very happy customer.