That's actually normal. Unfortunately, depending on which software you are watching your temps with, most read the Ryzen CPUs at +10C over their actual temps. So when you see 30C, it is most likely around 25C. As for the spikes, water cooling or AIO cooling simply moves the heat through the water, meaning it can appear to spike from time to time as warmer water hits the cpu block.
Now if you were seeing spikes of 20+C I would say you may have air in the lines, but 10 is about the norm. I watch my 1600X on an AIO Antec H2O 620 spike 5-10C at idle.