lscpu is a simple shell command from the util-linux package which gathers information about a systems CPU from Linux's sysfs,
/proc/cpuinfo and other available sources and presents that information in a nice overview.
lscpu will, without any command-line options, show you CPU architecture, the number of CPU cores, min and max frequencies, available CPU instructions (lscpu calls them flags) and known CPU vulnerabilities.
lspci has some command-line options which may be specially useful on dual-socket or many-socket systems.
--online will limit it's output to online CPUs and
--offline limit's it's output to offline CPUs.
The lscpu manual and
lspcu -h will show you all the available switches.