A pc only draws what it needs, no matter what psu. So at idle you'll see very low draws, 50w or less at times. No big deal for any psu. Light usage even on a RTX2080ti and 9900k is the same, only using a fraction of what's available at the psu. It's only when running high % use, hard driving the cpu and gpu that things change. Sudden spikes can over draw smaller psus, psus pushed to limits can fail to supply enough voltage or amperage so wattage draws from the others, creating issues, even total failure where the gpu shutdown due to lack of power. It's simply bad news all around to use an under-rated psu.