How differently from Linux kernel does a typical Unix kernel (System V, Free BSD, ...) implement processes and threads?

In my previous post , about the Linux kernel, - the structure task_struct represents threads i.e. light weight processes, but not processes. - processes are not represented by any structure, but by groups of threads sharing the same thread group id. I was wondering how differently or similarly a typical Unix kernel (System V, FreeBSD, ...) implements processes and threads at a high level? Thanks.