First of all, welcome to the forums! I'm the leader of WNxGES and its servers, I can give you a few tips and feedback here.
1) RTV is pretty much the only plugin (or add-on like you call them) needed for the community, others like gamemode votes, or radar votes aren't needed in my opinion since there will be admins around now and then. ges-stats is not released and only WNx servers have it for now, it was made by one of our members (using HLstatsX:CE engine) , and I'm not sure how easy or hard it would be to open it for the whole mod. Anyways, I recommend to keep the plugins limited and don't add too many of them.
2) A Steam group would be enough, I think. Unless you want to create a web and practice.
3) There are already monthly events on Troy's server, but not tournaments. I like tournaments. (also anyone can have a colored chat name if you know how
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4) GE:S is more fun without teamchat in mics, there's nothing that requires "tactical" gameplay and most of times the mic is just to have fun.
Personally I have my prefered server (I think it's obvious which one I prefer...), but if a server is well done I would go there sometimes.
About helping, I can always give feedback. Also don't give a lot of admin access, having a few admins that are active is enough and keeps everything more easily manageable.