Peace lily droops every afternoon, is this normal or dramatic?

If it droops during the warmest brightest part of the day and recovers later, it may be losing water faster than the roots can move it. Try moving it a foot farther from the window for a week.

Check whether the window area heats up in the afternoon. A plant can be in indirect light and still get hot air or radiant heat from the glass.

Peace lilies are dramatic, but daily drooping is still information. If the soil is damp, do not fix it with more water. Change the light or heat first.

Also check the root ball. Sometimes the outer soil feels damp but the center is dry and compacted. If water runs around the root ball instead of into it, the plant can wilt while sitting in a damp pot.

Mine did this when it was root bound. It needed water constantly because the pot was mostly roots. I repotted one size up and the daily collapse stopped.

Take notes for a week: room temp, soil feel, time it droops, time it recovers. Patterns make this easier than guessing.