Not sure what shower you have, but if it is a typical PP, there are no O-rings involved. On any stem which has an o-ring stem seal, there is nothing to "tighten the packing". O-rings do not work like that. You are describing a stem packing gasket and packing nut. Some lubrication is needed on the packing and the stem, which will allow you to tighten the packing nut adequately and still be able to turn the stem. Use waterproof plumber's grease or silicone faucet grease.
Danco is a generic parts brand, but actually the quality is usually good. However, you will get an almost universal recommendation on these plumbing forums to use Original Brand parts when available, which for PP they are. For just a few dollars difference, why chance a hassle?