Will I ruin my dropper from the rubbing of the strap of the saddle pack? Wrap it in insulation tape?

You’d have to wrap the dropper or you’d still have rubbing, but then you’d need to make sure the tape wouldn’t be in the way when you drop the saddle

I use an enduro collar on my reverb, set to give me a few cms of drop.

Bag is secured above the collar with a bit of synthetic chamois taped on. Seems to hold the bag, but not caused any issue with the post so far either.

https://www.wolftoothcomponents.com/products/valais-25
Might be an option depending on your saddle bag straps

I wrapped a tonne of insulation tape around my dropper. I basically made a ghetto version of what scotroutes links to above.

Not pretty but it worked fine.