No. Every wound is a separate mesh placed just above the surface. There are no booleans and no edits to your model. Delete the wound or the BU_Wounds collection and your mesh is untouched.

Yes. If your mesh has an Armature or other deforming modifier, the add-on binds each wound with Surface Deform. If that bind fails on a tricky mesh, it falls back to Shrinkwrap and keeps the raised edges. For best results, draw while the character is in rest pose or a neutral pose.

The presets are sized for a real scale human, where Brush Size 0.008 m is about 8 mm. If your character is 20 meters tall or 10 centimeters tall, the defaults will feel wrong. Either scale the character to real size and apply scale, or just use the Mouse Wheel while drawing to resize the brush.

This is the wound and skin surfaces fighting for the same space. Select the wound, open Advanced and raise Surface Offset slightly. It also helps to draw on the final smoothed surface, since the add-on reads the evaluated mesh including Subdivision.

Yes, at any time. Select it and adjust Width, Depth, Edge Lift, Irregularity, Blood Amount, Blood Spread and the Advanced settings. To change its shape, click Edit Path, move the points and click Rebuild.

Yes. The material uses standard Blender shader nodes, so it renders in both engines.