This happens sometimes and I don't have an explanation for it. It is not a sign that you bought the wrong thing. Sometimes the tube just seems like it has extra diameter, even when it's inflated only enough to give it shape.
You want the tube to be in the tire without being folded over or bunched up. Those conditions can create stress risers that lead to failure, and in some cases also cause weird bulges in the tire. Usually what I do when I'm fighting against this concern is do my best to cram the tube in as evenly as I can, inflate the tire, deflate it, maybe go through a few cycles of that, then deflate it again and pull the tire to the side without unseating it to check how evenly distributed the tube is. Usually it works itself out doing this. Talcum powder is a way of encouraging it to work itself out that could be useful in extreme situations. You can either shake it into the tire all around or put some in a baggy, put the tube in, and shake it to coat. I've known some mechanics who always do this because it only takes a second and makes the tube more cooperative to install, but I don't bother.
Don't get smaller tubes to address this, just stay with tubes that have a nominal size that matches your tire. This is just a quirk of some tubes. If you just can't get it installed without a folded or bunched up section, try a different brand.