Yes. Plugins need to work in our networked environment and have simple configuration options.

Looks responsive and degrades gracefully to the open state on mobile.

No. You will / may need to learn basic css to override the template.

In this case inserting the following into the customizer made the open/close symbols show up more clearly: +/-

.c-accordion__title::after {
  color: white;
  font-weight: 600;
}

Looks like it. The developer answers support requests and has recently updated the software, which is an indication it won’t be an immediate security risk.

No. Premium plugins can be annoying for our users, presenting intrusive offers or conversely limited free functionality.

No. Some plugins have way too many config options or simply too much functionality, which is rarely used or just too difficult for the average user.