My suggestion would be to say "clicks another X times/second," or "provides an additional X CPS," something like that.
The one other idea for UI would be indicators for what's needed for the next instrument tier bonus (i.e. going from +1 to +2 RPS), and what's currently provided (does 40 new instruments provide [40 * 8] 320 RPC, [40 * 16] 640 RPC, or is it [10 * 1 + 10 * 2 + 10 * 4 + 10 * 8] 150 RPC?)
And a third, idle thought: if we hold on to the plants (by completing the tree), why not give future rounds a 'prestige bonus' based on the branches taken (either a passive +X to either stat, or a multiplier), so it's easier to see all the combinations.
...And #4: have an indicator on the mutations list to show which ones haven't been collected yet.