Hi & welcome!
I would encourage you to trim the roots if you find a pancake of them at the bottom of the root ball, and/or very long, circling roots. I've always done that when repotting and trees always respond with a flush of fresh, new growth because the roots are again able to grow freely. Trimming excess roots will also make removing the rest of the old soil easier. This is also how bonsai trees are kept alive for hundreds of years in those tiny pots.
Potting-up (putting undisturbed root ball into new pot with more soil around the edges) can yield unwanted results, like excess roots rotting (and would be diagnosed as "overwatering.")
Dracaenas are known to be sensitive to fluoride in tap water, which can't evaporate, so whenever possible, using rain, distilled, or condensate from a dehumidifier or A/C can help keep your tree as healthy as possible, which will result in the best possible looking foliage. Don't stress about the oldest leaves because Dracaenas are constantly in the process of discarding them as the trunk lignifies.
An unglazed pot can also help keep your tree as healthy as possible, since roots are able to access oxygen all around the inside of the pot, even if the soil is dense and mostly airless. Roots need oxygen & moisture at the same time to function properly, stay healthy, and deliver moisture to foliage.
