Proton VPN review
Proton VPN's browser extension works with a free Proton account. The Windows app covers other programs on the computer and gives you two ways to handle a dropped VPN connection.
Decide whether you need the whole device
The extension works on Chrome and other supported Chromium browsers, as well as Firefox. Proton's help page says there's no Safari extension. If you switch to another browser or open a separate chat app, those connections sit outside the extension. Firefox also needs a separate setting to send DNS requests through the extension. Planet VPN also separates browser extensions from device apps and has a dedicated Opera listing in its download menu.
Pick how Windows reconnects
Proton describes two Windows kill switch settings. The regular one blocks internet traffic if the VPN drops unexpectedly. The advanced setting keeps the computer offline even after you disconnect it yourself or restart, until the VPN connects again or you change the setting. I'd read that distinction before setting up a laptop I sometimes use without a VPN.
Anabel’s take
I'd use the extension for a browser I keep separate from work. On a laptop where I need the desktop app, I'd start with the regular switch so I can still go online after disconnecting on purpose. I'd choose the advanced setting for a machine I want to keep offline whenever the VPN is down.