Chromebooks make heavy use of containerization, which increases RAM usage.
From my experience, Chrome OS still runs relatively well on low-end processors like Intel's N-series Celerons and ARM-based MediaTek chips. However, RAM is becoming a critical bottleneck for the operating system, especially on models with 4GB of memory or less. On the Lenovo Flex 5 with 4GB RAM, Chrome OS was using half the available memory with only a system monitoring application open. As soon as I opened a few tabs, the laptop ran out of RAM and began using swap space to keep everything running. SSDs are not as fast as RAM, so moving processes in and out of the swap space causes the entire operating system to slow down.
Earlier this month, I had the chance to review Lenovo's new IdeaPad Flex 5 Chromebook. It's a great machine, with an excellent build quality and