Depends on settings. If I run 640x480, I can do 18 without even close to maxing my system.
This is with an i7-6800k and a GTX 1080Ti, both watercooled but not overclocked.
However, bump it up to 800x600 and there start to be fps drops before 18 chars.
At a resolution that looks nice to the eyes, your limits are reached much sooner.
It's not a question you can easily answer, and even if I gave you an exact answer in terms of clock speed, you wouldn't be able to interpret it. Make sure you have a powerful, multi-threaded processor if multiboxing is a priority.
Finally, 'gaming' laptops are not for gaming, they're for parting idiots and their money. If you want a good performance/price ratio, look at a desktop.