Paradox Regarding the performance impact, I recommend referring to the Metrics view page in the Spine User Guide: https://esotericsoftware.com/spine-metrics#Attachments
As explained there, simply having an attachment visible may not affect rendering performance. For example, nothing is rendered for a bounding box attachment.
What Erika does at around 50:55 in the video is hide region attachments. Doing this reduces the Vertices, Vertex transforms, Triangles, and Area metrics. Of these, Vertex transforms is the metric that directly relates to CPU usage.
You can see this clearly by keeping the Metrics view open and observing how the values change when you actually hide an attachment. When an attachment is disabled, you can see the changes in the metrics mentioned above. However, if you simply make the attachment transparent by setting the slot color alpha to zero, you should see that those values do not change.
