Torque Wrench required for trainer cassette installation? I have a new trainer arriving on the 29th and obviously this will involve either using my existing cassette that’s still on the wheel or a new cassette to put on the trainer.
As my existing cassette has already run the same distance as the existing chain I’m thinking of using the existing cassette.
Now removing and installing the cassette doesn’t seem too hard and I’ve ordered the relevant tools

Chain whip
Cassette tool

How important is a torque wrench on this?
I think I remember somewhere that the R7000 cassette is 40Nm, or roughly 29 ft-lbs.
Do I need a torque wrench or is it a case of being tight is good enough?
Looking at the trainer install video the guy literally does it up with an adjustable wrench. This got me wondering how important is a torque wrench in this instance?
Install Video
Skip to around 6 minutes for the cassette installation
How important is torque wrench on this?

It's not important at all.  The cassette lockring just has to be tight enough to not come off as it's not doing anything other than keeping the cassette from sliding off - some cassette lockrings are even make of aluminum.
Use a long wrench and put a bit of force behind it and you'll be fine.