The 3D Sphere relies on your computers CPU and GPU to create and display the model and dynamic lighting. Where possible, the hard work is handed off to the GPU, which can handle tasks at high speed and in parallel.
Unless your hardware or operating system are very old, you should be able to find an up-to-date version of your browser, or switch to an alternative that can be updated.
This site has some good guidance: browsehappy.com.
You can check your system's WebGL capabilities at webglreport.com. Your system should have support for a maximum texture size of at least 8192. A higher number indicates a more capable system that is likely to perform better overall, but the software does not use textures larger than 8192 at this time.
The software has been developed and tested on a Mac that achieved a score of 473 on Basemark Web 3.0. On moving the camera on the 3D Sphere page with Sun, Moon and Milky Way enabled, the software consistently achieves 60fps (frames per second, tested April 2021, version 2.5.1), which is the ideal goal for web-based 3D software.
If animation on your system appears jerky or inconsistent, you may wish to run the free benchmark test on Basemark linked above to check if the computer/browser is fast enough.
You can also disable Sun, Moon, and/or Milky Way if you don't require all to be enabled for your planning work - that should improve the number of frames per second during animation. Disabling the 3D Terrain may also improve performance.
When maps are enabled in the Sphere page, you will see some increase in data consumption relative to using the regular map page as the 3D sphere loads tiles at a higher resolution than the regular map, so they are not reused, even when viewing the same geographic region. Once viewed however, subsequent loads of the Sphere will reuse the map tiles from your browser cache - they typically remain available for a few days before expiring.
When the 3D Terrain feature is enabled, you will see additional data consumption as the elevation data is downloaded. Typically this will result in around 2-3MB of data being requested for each unique area.
If data consumption is a concern, consider disabling 3D terrain until you have found your location of interest.