Shopping Advice: HP Spectre x360 Heating and Throttling?

Hi. I'm traveling to the US and will be buying a laptop. My absolute max budget is $1000.

I need to be able to run MATLAB comfortably and I would love to be able to play a few games, though I don't mind not being able to run the latest ones. GTA V would be absolutely ideal if I could run it at least at minimum, to give you an idea.

Anyway, these are my choices so far. They are all Skylake laptops.

HP Spectre 13 x360
My top choice is this one. For $1000 I get i7 Skylake, 8gb RAM, 256 SSD and amazing looks, weight and size.

Dell XPS 13 9350
I can work with the 128 SSD if need be, but I'm not convinced about the i5 (i7 configurations are too expensive for me).

Lenovo Thinkpad Yoga 14 (460)
Dedicated graphics is great, but there's the extra weight and bulk

However after reading several reviews and reports I'm really worried about the Spectre generating too much heat and even throttling the CPU when taxed. This is the reason why I'm even considering the XPS and the Thinkpad. If it can be confirmed that heat is not that big an issue with the Spectre I will most likely buy that one.

Regarding the other two, do you think an i5 in the XPS is enough for my needs? Do you think the extra bulk in the Thinkpad is worth the dedicated GPU?

Of course, if you have other suggestions within the price range they're welcome!

Thanks!