Hi there! Keep in mind that actually using OpenGL (that is, using low-level OpenGL instructions, drawing inside the renderOpenGL() callback, etc.), and merely attaching an OpenGLContext are not the same.
The latter lets you use the JUCE graphics classes (Path, etc.) but might not necessarily improve performance. For example, I have found that on Android it certainly helps but on MacOS it usually makes things worse. On Windows, it seems that Direct2D is what currently provides the greatest performance boost: https://forum.juce.com/t/direct2d-part-3/57410