Pin heatsinks? If so, Angle aluminum will suffice. The heatsinks should have holes in the sides for mounting.
Not quite as easy as that. First you have to know the efficiency of the CXB3590 then you have to know how many watts you will be running to it. Then you have to know the thermal resistance of the heat sink used. Once you know those factors you can calculate how many degrees over ambient temperature the LED will run. So you have the 50 watts part now you need to figure out the efficiency of the LED they should add that to the data sheets but they don't. Going to be around 60% is my guess so that would mean you need heat sinks that can handle at least 20 watts of heat. 30 watts gets turned to light 20 watts is heat. Now the better the heat sink the lower the cob will run temperature wise. This will always be over ambient temp their is no one set temperature the cob will run. So if the of heat sink calculation is 20 over ambient temps then a 25C room will have a cob temp of 45C, a 15C room will have a cob temp of 35C. Here is a link to a page that explains how to calculate for proper heat sinks. https://www.led-heatsink.com/thermal-calculation
They will provide decent performance. The difference between running cool and warm isn't really a game changer, it's just a way for the enthusiast to squeeze a little more light from a rig.
Pretty close to the max temperature plus acrylic breaks pretty easy. Polycarbonate might be a better choice as it is more impact resistant has about the same temp rating I believe.