Well, by small I was thinking smaller than that, maybe up to half of your env. It is big enough to consider Cohesity as better option, if there is enough resources available (money)
Still, it may be handled well by TDP for VE, if you are going to leverage some existing IBM licenses, or to upgrade a little upon them.
What is more important, if you go this way (TDP for VE)
Tape is not your friend.
You do not want operational VM backups residing on tape.
Tape may be used for another (air gap) copy, not for regular backup / restore jobs.
The thing is, unlike SP+, TDP for VE does not backup VMs as complete images, at once. It cuts them in so called mega-blocks, pieces of (if I am not wrong) 128MB each.
With incremental backups you will have your VM images scattered on many tapes, so no tape streaming from there, but countless mounting, rewinding and so on.
Even worse, beside "mega-blocks", there is also a tiny pointer file for every one of them, which you need to keep on disk all the time, since if it goes to tape - your restores will last forever.
For VM backups, on TSM server side, you go with container pool, on disks. These are pools which do dedup / compress, and they do it quite efficiently, for VM backups you may expect up to 80% savings, or let say your ~120T will probably fit to ~30T of disk, or a little more.
Conclusion:
You should probably go with Cohesity, either directly or through IBM (they OEM it).
If there are existing IBM licenses that may be repurposed from SP+, and there are financial constrains, you may create proper solution with TDP for VE + ISP / TSM, but do not rely on tapes for operational backups.