As far as I understand it’s better to stay within 25 - 30% margin or PSU, because of you may have more latency on component failure with larger PSU that is used in 50% capacity than with smaller PSU that is used in 75% capacity. Like if your system power draw is 500W, and one component is failing, the protection will kick in when power will be exceeding 650W for smaller PSU or 1000W for bigger one, that is already double of your normal system draw.
Strangely enough, my ASUS Thor 750 rarely shows power draw more than 350W, and my rig is
ASUS Cosshair Hero VII
AMD 3700X (OCd to 4400) - I had 2600X (OCd to 4000) before
2x8 GB Corsair PRO 3200 DDR4 (not sure how it’s OCd as I just installed 3700x yesterday)
Palit 2080 Ti OC
NVMe 500 GB Samsung EVO 970 HDD
3 x 500 GB Samsung EVO 860 SSD HDDs
ROG Riyo 120 (I know it’s too small for 3700x, plan to go to new case and Ruyjin 360)
140 mm fan
2 x 120mm fans (push/pull for Riyo)
32" 2560x1440 curved Samsung screen
one externally powered USB hub
the PSU calculator gives me 605W, OLED on THOR 750 in gaming (Rage 2, ED, Metro Exodus, THE Forest, DOOM, etc - all on ULTRA settings) - hardly goes over 350W, normally it stays in 275 - 300W, and I never seen it goes over 400W. In desktop mode it runs around 65 - 120W.