The Business Insider office has an incredibly fast internet connection with very low "ping," or latency, which is directly related to lag. When I played "PUBG" while plugged into the office's ethernet connection, there were noticably fewer stutters.
It's a sign that the stutters I was experiencing were more likely from my WiFi connection rather than the GeForce Now app. Still, my WiFi router is a recent, powerful, and expensive model – I'm using Netgear's Orbi mesh WiFi system, if you're wondering — so it was a little surprising that I was experiencing as many stutters.
If possible, it's best to connect your Mac to an ethernet connection rather than WiFi to minimize stutters.