I doubt the LC will be quieter because the Nitro+ has fans running 1400-1500RPM or so.
"We start with a small radiator and one fan. Using Turbo mode in AMD's driver results in a power consumption of approximately 316W throughout the test scene, and the thermal outcome is barely acceptable. If we drop the fan speed to 1000 RPM or less, then we find ourselves beyond the 60°C mark. There's just no way to enjoy cool temps and quiet acoustics with this configuration." --- this isn't LC but a copper radiator with copper block (Alphacool Eiswolf).
100% Fan speed = 3300RPM , so you'd need 50% fan speed or less and the review states that at 50% fan speed it's louder than quite a few cards including Nvidia's GTX 1080 FE.
"For fan noise, this is a rather unique setup as both the pump and fans are a noise concern. Though when I did my testing it was surprisingly quiet at both high and mid fan speeds. The fan speed chart only shows the pump speed though, I think the 120mm fan on the radiator was running lower to get those numbers. It should be noted though that later in my testing our pump did start to develop a rattle."
^ another review with Vega64 liquid louder than GTX 1080 FE