Sort of both.

> AmigaOS was a pre-emptive multitasking OS

Yes, but without memory protection.

> whilst PCs had to wait for Windows NT/95.

While Windows 2 on an 8086 could pre-emptively multitask DOS apps, so long as they all fit into 640 kB at once. Windows/386 could do it in extended memory.

The innovative thing in W95 was doing it to Win32 apps as well.

OS/2 in 1987 or so could multitask OS/2 code on a 286.