Point of impact shift shooting with a bipod or a backpack and bipld height?

Standard hunting ranges to a rifles 3” POI not gonna matter much. Start pushing distance and muzzle flip you have no control of over a back pack versus controlled push on bipod does make a difference.
Depending on caliber and bullet weight. That can be as close as 300 but typically in 400-500 range scenarios.

Just practice how you plan to hunt.
Thanks for the suggestion! Can i ask why? I had a 6-9 harris on a 22 cz and i lovednshooting it prone.. i don't remember if i used it with full extended legs but i don't think so. couldn't the 9-13 be too tall for some applications?
When you’re lying down in a hunting situation it’s not often level ground with a level shot. And there’s grass etc to get over. I mostly carry my 9-13 pre extended about 2” as a default setting. In more mountainous terrain I attach a 12-25” as it allows a much broader range of shot angles, particularly steep uphill or steep downhill. 6-9 is best for on the bench.
I personally haven't noticed any difference in my poi but I see where it might happen if a backpack is spongy. Some backpacks offer an optional bag rest that mollie attaches to the pack. Personally I like options simply because every hunting situation is going to be somewhat different. If you don't mind a little extra weight you can have a bipod on the rifle, a bag rest on your pack, and a tripod in your pack if you have to make a standing shot. Just keep in mind, " a man has to know his limitations " practice will reveal the answer.