Mickael Istria

CMS Garbage Collector has been deprecated for a while (since Java 9) and Eclipse IDE is supposed to work for any Java version >= 8 these days. So it cannot move back to CMS GC.
What would you suggest as GC options for the Eclipse Java IDE.

4 to 5 days in getting a new Eclipse running??? You must be kidding. Either it's very exaggerated or it means that your staff se quite slow and isn't good at documenting what's good for them and capitalizing on knowledge... I can understand that Eclipse setup can require some time if you need external tools (often), but really even installing 20 different plugins from marketplace doesn't take more than half a day.
Also, if you have to multiply those hypothetic 4 days by the amount of users, it just means that you're missing a point in the principle of factorization. You can just install Eclipse on a machine, install plugins, and share the output folder with everyone. So you do the effort only once.

Also, there are many providers of "plugin sets" (such as STS, named here; or JBoss Tools/JBoss Developer Studio or Nodeclipse...) that install a consistent set of plugins together targetting a specific user-story.

I would like to give some hope about JavaScript development in Eclipse: the JSDT project is currently being more actively developped to match "modern" usage. Also, there are some nice plugins that already make JS dev much better inside Eclipse. I recommend to look for "tern.java" or "eclipse-angularjs" projects at GitHub, that provide a much better experience.

As already answered, il mainly and only a matter of personal taste. I also prefer Eclipse theme because it integrates better in my OS theme.

That said, there's a 3rd-party plugin for Eclipse called "Jeeyul's Chrome Theme" which allows to easily customize Eclipse theme. It's a must-have if you're interested in Eclipse and not happy with default look.