The issue here is PROBABLY that AV2000 kit is wired half duplex, not full duplex, and relies on relatively coarse, clunky timing windows, at least for something as adaptable as gaming which wants as low latency as possible; both in terms of the video, but also the return path for controls and other inputs. This can cause problems with rapidly alternating bi-directional traffic which the older standards struggle with (fundamentally AV2000 is from middle of the last decade). Agility/low latency are a key requirement of real‑time gaming, and those clunky, relatively inflexible windows result in jitter. The stutter Chef mentions was likely error/timing correction or client/host resync caused by slight desyncs rather than raw bandwidth limitations; your 600Mbps are more than enough for that - hell most people push less than that to VR headsets
One of the key benefits of the latest/current G.Hn standard isn’t peak throughput, but it handles scheduling and busy environments in a much more agile and adjustable way, and typically doesn't fall over in scenarios where older Powerline standards would, like difficult or noisy conditions. While still technically half duplex, it uses much shorter windows, more granular scheduling, and faster turnarounds, allowing it to behave much more like full duplex for realtime traffic, reducing that jitter to something more tolerable. I know that sounds weird, but in practice it can simulate full fat, bidirectional duplex LAN behaviour far more effectively than older standards, even if its not truly full duplex. Compared to Homeplug/AV1/AV2 standards which used larger windows primarily optimised for raw data transfer speeds, streaming and internet usage rather than mixed or real‑time usage like VOIP or realtime online gaming, G.Hn is just considerably more responsive.
Even if bandwidth and average latency are fine on AV2000, its more clearly half duplex nature was likely the limiting factor there, as that has traditionally been the main drawback of powerline networking (along with throughput being considerably lower than the headline speeds). When powerline was at its peak about 10-15 years ago, Wi‑Fi was FAR less mature (read: It was bloody awful for gaming), and powerline often performed CONSIDERABLY better in real‑world use. Since then, WiFi has advanced massively in terms of smarter, much faster scheduling and lower latency contention handling, and much, much, MUCH more capable multi channel routers (and MUCH better ISP supplied routers) etc — despite WiFi also being half duplex — which is one reason a proper hardwired (full duplex) LAN connection is still superior to both.
TLDR: You really want to have G.Hn units if you're pushing this kind of use over powerline, they're just better suited and a more modern standard, to the point that throughput might be the same or lower, but jitter and flexibility are better. They're far more aimed at real world, mixed-usage, and non ideal circumstances, whereas the older AV standards expected everyone to play nicely and be willing to wait - essentially British scheduling as opposed to Japanese, which is far more granular haha
