I have used NordVPN for a 2-3 years now, maybe more. I use it on my Mac mini, iPhone, and iPad. It performs very similarly on all. If I run SpeedTest there is somewhat of a degradation compared to unprotected, but that is expected. I have gigabit fiber home internet, and typically, without using NordVPN, get in about 500Mbps downstream and 400Mbps upstream. This varies a lot though. With NordVPN I get around 350/225 for down/up. This is expected and acceptable.
I have used it extensively in the USA, and occasionally, just to try it, I will use servers in other countries. I don't stream movies, and an not a gamer. On some recent travel to New Zealand and briefly in Australia, it worked fine using servers there. I was usually not on Wi-Fi. I didn't run Speedtest, but my experience was not noticeably different from not being on VPN.
There seem to be some organizations that can tell you are on a VPN, for example, Amazon. This is a problem that Nord folks cannot seem to solve. It isn't a big problem for me, although it is inconvenient to have to pause my VPN. If it becomes widespread that some places won't work when connecting via NordVPN, or perhaps any VPN, it will be a big problem. The entire point of VPN is protection and anonymity.