Marshall,
I own a Ruger 7MM mag and I ONLY shoot Winchester Fail Safe bullets. I dropped a mature 6x6 bull elk with 140 grains with one shot. I am also going bear hunting on August 11th. I will be trying to take a bear with my bow, but the 7mm will be by my side just in case I don't get the opportunity with the bow. I will use the same 140 grain bullets that I used with my elk. I trust it will do the job. The key to all situations, though, is shot placement. If the shot is good, you have nothing to worry about.
Now for coues, I would not use 160's. I shot a my first coues at 125 yards with 160's. The bullets traveled so fast that they did not expand and went right through the deer. After the first shot, the deer never even flinched. After the second shot, he just started walking down into a draw. I had thought I missed both times, but went over to check just in case. He was dead in the draw. Upon dressing him out, we found two holes about 2 inches apart. Bullets went clean through. A coues deer is just not dense enough for the bullets to expand.
So to answer your questions, the 160's are fine for bears. No need to get the 180's. For a good bullet for both, I would shoot the 140's.