The best alternatives to Taskbar stats are Istat Menus 6, Barsoom 2, and Stats. If these 3 options don't work for you, we've listed a few more alternatives below.
iStat Menus covers a huge range of stats, including a CPU monitor, GPU, memory, network usage, disk usage, disk activity, date & time, battery and more. All in a highly optimised, low resource package. iStat Menus is highly configurable, with full support for macOS’ light and dark menubar modes.
Stats is an application that allows you to monitor your macOS system: - CPU utilization - GPU utilization - Memory usage - Disk utilization - Sensors information - Battery level - Network usage
StatusBuddy is a simple app that shows an icon on your Mac's menu bar. When an Apple service is having issues, the icon shows a red badge and you can click it to check what's going on.