I have answered your questions below :
1) I'm thinking of signing up with EZA, just wondering if it takes them a while to approve your articles? ....I believe they check each article manually.
When you signup with them your author status will be "basic" and you can submit up to 10 articles there. They may take up to 7 days to review your articles, although current review time is kind of lesser than that.
Yes, they review articles manually.
2) Would there be an dramas if I submitted 20 original articles in the beginning?
You can't submit 20 articles altogether. You will have to wait till your first 10 is approved. If you submit 5 articles and if they reject 3 out of 5 asking you to do changes, then you have only 2 submissions left. That means when you resubmit an article your count goes down too.
Submit your first 10 best quality articles. Make sure you read their guidelines before you do this. Once they approve first 10, then you can send them a message requesting platinum status. You will have to write why you think you deserve a platinum status. Now, DON'T go and write you need traffic, you need to make money etc. Write something like " I like to contribute good quality content to my readers. Writing is my passion" and all sort of shitzz. If you are lucky, you will get platinum status. If you get, then you can submit unlimited number of articles and review time will be less than 2 days.
3) Once my article is live, can I go back and edit it again? And if so will it be taken off the directory for a manual review again?
Yes, you can edit. Yes, they go back for manual review.
Hope this helps
Tom