Sometimes raising core clock is needed to stabilize higher vram clock and other way around. You just need to benchmark and test how your card behaves. You dont need to touch the core voltage, just keep it default and your 100% safe.
MSI afterburner is what i use, just max out power limit first and then start testing with raising core clock, when you start crashng or artifacting drop your oc -15mhz. Then start with memory clock and do the same, but when you get issues with vram drop -25mhz from first artifact / problem.