There are three main issues:

• Epic Fight added explicit support in Epic-Fight/epicfight#2112, but lock-on is still not fixed, and Shoulder Surfing adds a config and a mixin on Epic Fight to fix the issue. This creates tight-coupling between the two mods, which is hard to maintain. The Epic Fight team plans to introduce breaking changes soon. My suggestion is to remove the Epic Fight integration from Shoulder Surfing as soon as I add explicit support from the Epic Fight side.
• The Shoulder Surfing X Epic Fight lock-on integration is optional, but IMO it shouldn't be even a config, users probably don't want to have the option for a buggy behavior. When adding explicit support, this config won't be needed anymore and can be deprecated.
• The player can't lock on target when the Shoulder Surfing camera is decoupled, but the crosshair aims at the entity. This is not fixed, even with the integration enabled.

I do plan to take over this issue, but I may need more time, so please consider keeping it open until it's fixed.