Stick with rubber bushings! The poly is a harder material so it’s less forgiving. I’m by no means an expert. I’ll leave it to someone else, that’s more knowledgeable on the subject, to break it down Barney style for you. I just know that about 99% of the time, OEM rubber bushings are recommended. I do believe I seen a thread here somewhere talking about how poly is better or acceptable for the front/rear anti-swaybars, but I could be mistaken...
And yes as for your question about the T-case shifter cable. It replaces the OEM linkage completely. Most here will recommend Savvy. There is another common shifter cable as well, but I can’t remember the manufacturer name. It is very similar to the Savvy cable shifter.