The main problem you run into here is that you use a sculpted mesh. Such a mesh is created for portraits and to get the overall shape of the character. It's not suitable for texturing and animation because it's very dense and requires a lot of data and calculations.
For animation, you need to create a lightweight version of the mesh. This process is called retopology.
If you enable the wireframe overlay you will see the difference between the sculpted mesh and the retopo mesh. It's roughly 280,000 vertices vs 8,184 vertices.
I've done the retopology for the head. The rest I've frankensteined from a basemesh, feet and hands. I've noticed that the hands of the base mesh have a few triangles and the feet have a few 6-star poles. No biggy, they are at spots you will not see them and where the mesh does not deform a lot. But I've decided to replace them. In hindsight, I could have simply used the MBLab body.
You can use the Grab, Elastic Deformation, Smooth and Pose brushes from the Sculpt mode, and a Shrinkwrap modifier to shape the base mesh according to the sculpture. With vertex groups, you can limit the effect of the Shrinkwrap modifier to certain areas. Sometimes it creates glitches but with the Snap option enabled, you can fix them manually in Edit mode. Just grab the bad vertex and it will snap to the nearest face. Clothing can be adjusted in the same way.
Also, consider reducing the number of vertices of the eyes and the eye-glass objects. They have 35,000 and 44,000 vertices for each eye. With the Decimate modifier you can Un-Subivide the eye 8 times and it will have only 157 vertices with 12 segments. Add a Subdivision Surface modifier and it will look fine with only 5000 vertices at render time (level 2).
Before you start to rig the meshes apply the Rotation and Scale to the objects (Ctrl+A) in Object mode. For the body mesh and the metarig also apply the Location. This will reset the values in the side panel to (0°, 0°, 0°) and (1.0, 1.0, 1.0).
Also, check the Face Orientation. Applying a negative scale (eyes) will flip the normals and the object is inside-out. You need to flip the normals in Edit mode (Alt+N to correct them.
The Parent To > With Automatic Weights works well except for the eyelids and the mouth. These parts need manual weight painting. Also, the eyeballs, upper and lower teeth need to be children of the eye/teeth bones (Parent To > Bone in Pose mode). If you use Blender 3+ make sure you have upgraded the face rig. There is a button near the Generate Rig button to do so.
You can turn off the Subdivision Surface modifiers anytime when you need to reduce the number of vertices in the viewport to get better performance. On the Render Properties there is the Simplify option that can disable all Subdivision Surface modifiers when you set the Max Subdivision value to 0.
One last thing. Her arms are too short. The distance between the fingertips in T-Pose should roughly equal the character's height. She is 1,65m tall but her arms are 1,40m short. But no worries. The low-poly mesh allows you easily to make her arms longer.