does your bike presently have a rear rack?
Ive toured with all kinds of variations of bag distribution, and here are a few thoughts.
First, the Tara is a really good solid rack. When I got mine I noticed the diff compared to my old front rack. To be fair, diff bike that had a much more solid front end, and also I removed the orlieb inserts and enlarged the tara's tubing with rubber tubing and tape so that there was no play or movement of the bags over rough roads. I also have wider tires, so the proper pressures for the surfaces mean less jarring at the front.
yes, the steering is slowed down with heavier front panniers, but its not all bad, its just different.
I used to always prefer a lighter steering front, and for some conditions its nice to have rear panniers so you can move the front faster and or pop the wheel easier over obstacles, but then you still come back to more weight on the rear wheel, making life harder on it and its spokes--but Im a light guy, so less of a factor for me in this case.
and as always and as others have said, heavier stuff lower down in panniers is the rule of thumb.
if your rear rack is still on, it can be an easy backup with a small dry bag and a bungee for extra food or whatever after shopping if needed.