Need help with snapping settings

It's not your fault. To this very day (latest Illustrator 2023 version) the precision of snap is directly affected by the level of zoom. Vector program or not, the more complext the object, the worse the snap mistake. If I remember correctly, years ago someone explained that had something to do with optimisation but I just can't see a reason for vector rounding. Oh, and  snapping always works in InDesign.

It's awful, I know. You always have to double check. Even when cutting simpe forms (like cropping a circle from the middle with a point-snapped square) you might get micro offset points.

When trying to snap a point to a guide, don not clik on the path, click on the point or corner, hold and drag, when it is on or very close to the guide, or other point, you have to see that the cursor, an arrowhead, turns from black to white.

In that instant, release the mouse.

You can now zoom and check it is exactly snapped or on that guide, or both corner points are on the very same place.

When doing what? Creating anchor points? Moving an object? ...