Undervolting works great with reference cards. It a great way to lower temperatures and power consumption. This is not a reference cards so it might be difficult. Let's see what we can do.
Do not try SmartDoctor. I just can not explain how shitty program that is.
Lowering memory to 150MHz is safe. I always run my cards with memory at 150MHz. Stable for months.
About undervolting. I'm not sure if this works but you can try adding the following text to your hardware profile file (.\Profiles\ VEN_1002&DEV_6899&SUBSYS_03 481043&REV_00&BUS_1&DEV_0&FN_0) I'm not 100% sure of that file name but let's hope it's there.