That "2.2GHz" is just the base clock. Unless the system is overheating, it should be able to automatically ramp up to higher boost clocks when under load. That processor's maximum turbo frequency is 4.1GHz for lightly threaded workloads, though the actual turbo frequency may not be quite that high due to heat constraints in a laptop, which can vary from one model to the next, and depending on the workload.
As for whether that particular system is a "good deal" for $879 refurbished, it's probably a decent-enough option, but it's worth noting that there are other new laptops around that price range offering similar hardware as far as the major components are concerned, and it might not cost much more to move up to something with a faster graphics card, which can make a big difference to gaming performance. As far as gaming systems are concerned, a 1050 Ti is kind of toward the lower end, at least for running the more demanding games at good settings.
A gaming laptop could be fine if you need to move it around regularly, but be aware that a gaming laptop with a 17.3" screen might not be the best option for mobility if you need to carry the system with you on a daily basis, due to its size and weight. I believe that model is close to 7 lb (3 kg). And if, on the other hand, you plan on leaving the system on your desk all the time, you would likely be better off putting together a desktop system instead, where you could get more performance for your money.