Veracrypt system encryption on ssd, do i have to trim the disk right after finishing? how?

i want to encrypt my os that is on ssd (windows 7, x64, mbr partition style).
From what i know veracrypt will encrypt the whole disk, not only the actual data.
not only! it will “fill” the empty space (inside the decrypted disk) with random data to allow hidden os/containers.
This means that the ssd will think that the ssd is full and wear leveling will be limited, thus decreasing the life and speed of the ssd.
can a solution be write in the encrypted disk a very big file that fill the disk and then delete it so that trim will run and mark again most of the disk as empty? will it be one trim operation or more probably many many trim operations (one per sector) that might fill the trim buffer and failing?
does windoes 7 defragment also retrim the disk by sending trim operations at slow speed to allow the disk to process them?
or i have to do nothing and veracrypt will notice that it’s an ssd and encrypt only data and not the whole disk?
can someone point me to a solution inside the veracrypt guide?