Playing games like that will always heat up a device, regardless of what kind of ROM you're on. The severity of the heat can vary a little from ROM to ROM but it's always there. They're CPU intensive apps, what do you expect? Funnily enough the app that I find heats up my phone the most is Chrome. There is no real solution, apart from maybe underclocking your device but then your performance might suffer.
You need to understand that computing generates heat, and games that ramp up your CPU generate a great deal of it. PC's and laptops have pretty decent fans that run to expel the heat, and even they get pretty warm. Our mobile devices have no fans so they have exactly zero ways of transferring the heat from the device to the exterior air. I don't believe mobile phones are a very good platform for gaming for this exact reason.
If you don't want your mobile device to heat up, don't use it in such a way that it will. If you want to continue to use CPU intensive apps, learn to live with the heat.
Sent from my Evita
OnePlus One | crDroid/AK | TWRP 18.104.22.168
Do not PM me asking for assistance, that's what my Q&A thread is for!