The Unstable Totem will not be random - everyone will get the same thing - and it's equivalent to a Legendary totem for the production bonus (doubled).
The thing to keep in mind though is that the value of totems increases exponentially as the land is built out over time. For example, early on if you have a forest plot producing 10 Wood per day, then a Legendary totem will get you an extra 10 Wood per day. But once you have a max level building on that plot and you're producing maybe 10,000 Wood per day, then the totem is getting you an extra 10k Wood per day. So the Legendary totem effectively doubles all of the time and cost and value you put into the plot it's used on.
This is why these Unstable Totems are only $10 (vs $1000+ for a Legendary totem on the market). They only work the first 30 days, which is when the totems will have the least value.