Never personally used the Opera Browser's VPN, but after looking into it I saw
this article saying "...Opera has been known to sell its user data to advertisers for a profit."
I've used Proton VPN (As well as their great email service). If you only need a VPN on one device, maybe check out their free service. Been a while since I used it, but it worked well for me. And if you are looking for a new email service, check out Proton Mail.
Been a long time since I used Nord, but I know people who currently do and they have no complaints.
I'm currently using Private Internet Access, which is paid, but working very well for me. PIA has a lot of great features, such as preventing traffic from bypassing the VPN, automation, a bunch of protocol settings, blocking domains used for ads and tracking, and a bunch of others.