CGDive covers everything you need to know to retarget mocap with Blender.
Check out this tutorial series from CGDive (Todor Nikolov), which is a complete guide to retargeting mocap inside Blender. The tutorials focus on working with the Rokoko library of motion capture assets.
The three-module series looks at everything mocap and retargeting, including mocap resources, importing and exporting data, retargeting using Rokoko and Auto-rig Pro.