Is the Nuc using the Intel Iris Xe? Doesn't matter.
Yeah, still going to suffer from big heat spikes and graphics are going to be limited.
If your looking at an i7 nuc, for that money I think you can build a much better gaming computer. If your only playing CS:GO and older stuff like that, the Nuc will be fine. Modern games will batter a nuc.
My nuc 8 is decent spec, i5, 32gb ram, 512gb m.2 3500mbps read write and 2tb ssd. It uses the Intel iris 655. This was cooking just being a plex server in the standard case, granted everything is 10bit. Only now with new case which is basically a huge heatsink, does it run cool.
But hey, each to their own. It depends what games you want to play. What's your nuc build estimated cost? Around the grand mark? If you want a media pc then I'd go nuc. If your after a gaming/ all rounder I'd bang a pc together. You can still keep the size smaller than a full tower. Just make sure you can fit a decent graphics card into it. I can install gta 5 on my nuc to see what fps I get if you want?