Thermostats were only used to get the engine to heat up quickly to reduce emissions and reach operating temperatures. The main thing is radiator surface area and heat transfer coefficients of the radiator material, like copper or aluminum. If you can increase the surface area of the radiator, you'll reject more heat. Thickness by itself will not do this. It won't hurt, but it won't necessarily help. This is why some 3 core staggered cores cool better than 4 core inline cores.
You want the pump to speed up for maximum cooling. Never slow it down. When dealing with radiators, you want turbulent flows and when you slow flow down, you can lose turbulent flow. The mass flow rate equation proves this to be true. Same with the air flow side. So make sure you trap the air to go through the radiator and not around it. Make sure all the seals are in place and shroud if applicable. Push/pull electric fans with suitable air movement will do the job or make sure your fan clutch, if used, is in good operating condition.
180 or 195 is perfectly fine. 195 was used in most CCC types so as to get that cat hot quick and stay hot enough to reduce emissions without burning sh*t up. But as noted, once the T-stat opens, it's going to pretty much act more as an orifice.
All that to say.....your radiator configuration and air flow across it will determine how fast you reject heat, not the T-stat.