I've traveled Europe with Eurail passes several times now and swear by it being easily the best way to do the continent. Yes there are certain drawbacks such as reservation fees on certain routes but the positive FAR outweigh the negatives in my opinion, if for no other reason than giving you the freedom to decide where to go without worrying about cost and planning way in advance.
Deal is also going on at Klook with 5.5% Shopback. I have used klook in the past and they have worked just fine with no dramas.
I also definitely recommend the first class option if you're not sure. I took the plunge a couple of years ago and definitely found it worthwhile but people will have different opinions.
Is there a end limit on that activation, or is it just that it can't be used prior to September ?