25.0.1 (1/9/2019)
25. Removed: The Legacy D3D9 Theater View mode has been removed in favor of the ANGLE-driven Theater View which uses either D3D9 or D3D11.
MC should still be using Direct3D if available on a Windows PC. You might notice a very slight change in "snappiness", because ANGLE is now an intermediate component, but it shouldn't be much. If noticeable at all.
A log will tell you which backing renderer is being used. Look for "OGLCore" and surrounding OGL entries. It can theoretically also use Desktop GL as a backing renderer, but unless both D3D variants fail, it really should not get there, so I don't expect that to ever happen. Usually D3D11 is preferred if available, D3D9 used otherwise.
For example:
0003110: 9012: General: COGLCore::Initialize: OpenGL Version: OpenGL ES 3.0 (ANGLE 2.1.0.05c729f336ef)
0003110: 9012: General: COGLCore::Initialize: OpenGL Vendor / Renderer: Google Inc. / ANGLE (NVIDIA GeForce GTX 1060 6GB Direct3D11 vs_5_0 ps_5_0)
0003110: 9012: General: COGLCore::Initialize: OpenGL Shader Version: OpenGL ES GLSL ES 3.00 (ANGLE 2.1.0.05c729f336ef)
Check which renderer is being run on your NUC. It should be D3D11 I think, which would be better than the D3D9 the "Legacy D3D9" was using. There may be a slight change in GPU load which is what you are seeing, or more likely CPU load in handling the ANGLE translation layer. But your NUC with its Intel HD Graphics 620 should handle the load.
Make sure you upgrade your Video Driver to the latest. That can certainly make a difference with this technology.