Hi there!
Those kind of plugins performances depends a lot of the actual calculation resources of the performing hardware. In general, Rpg Maker is already CPU intensive - in some cases, I have seen NW.js performing worse on MAC as well -. Furthermore, the creation of the shatters Is based on delauanay triangulation algorithms that makes important calculations as well. On the hardwares I use (2018 assembled PC and MacBook PRO 2020) performances are good as shown in the demonstrative video.
About the hardware you use, not sure which Mac MINI hardware is, but if it's default version (M1 chip + 8GB RAM and no GPU), It could be possible that the execution time may suffer from both nw.js and triangle creation.
However, I'm planning to release in the future a small update adding execution delays for saving computational time in problematic hardwares. Furthermore, if the interest on the plugin from the public will be strong, I could try to release a new plugin version that uses GPU shaders instead.
Thank you for your feedback :)