No. An empty block will still be listed as empty and thus be TRIMed.
Even if your drive is encrypted, the drive itself knows nothing of the encryption, just where which data is (and which space isn't used at the moment). So it'll be fine.
As for the performance, I don't know how the impact might be. It would seem that certain optimizations in the SSD might not work, but I cannot figure which ones require knowledge about the actual data so there will probably be no impact from a storage point of view.
Note that encryption requires extra CPU cycles, so the impact might be noticeable there.