Depends how granular you want to get with CO and how close to the edge you are willing to run.
Me I adjust CO in increments of 5. If -30 isn't stable I drop down to -25. And I only use All-core.
There are some folks who tweak CO Per-core, you can either run an all-core load and check Windows Event Manager for which core crashed, or run a single-core load and set affinity in Task Manager to test each core one at a time. It's a cumbersome process either way and not one I'm interested in to eke a few extra MHz out of one or two cores for.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT