I remember when I first got into the hobby about 15 years ago, thermal barrier coatings were very popular. They've fallen out of popularity at this point for performance automotive gas engines as the gains are very small. Above about 2500 RPM the cycles happen so quickly there simply isn't enough time for very much heat transfer to take place through the head of the piston and combustion chamber surface.
Steve Brule noted on an episode of Engine Masters testing the effect of coolant temps on power, over his years of testing high-end race engines the reduction in power from higher coolant temps was due to its effect on limiting intake flow into the cylinders during intake stroke and exhaust/intake overlap. It wasn't due to heat transfer during compression and power strokes.
On that note when they tested iron vs. aluminum heads, the consensus was it wasn't due to differences in heat transfer in the different materials but due to hot spots in iron heads causing preignition. Smoothing and rounding off any and all sharp edges and unmachined cast surfaces in combustion chambers of iron heads is very important to help prevent that.