I trimmed and corner rounded quite a few decks in my time.
Not sure about scissors, I have always used the paper cutter; it's faster, and it did not let me down.
Well, in my haste I cut the titles of a couple of decks by mistake, and these decks were rendered useless, so I threw them away (Pirates, and Enchanted tarots) , and on another occasion I trimmed a deck (Sun and Moon Tarot) that already had smallish cards and incoherent borders, and the end result was devastatingly near tiny, the size of regular Lenormand cards.
But otherwise, and you can check my profile for trimmed decks, I am quite proud of most of my trimming work, particularly on oversized decks, and ones with largish borders.
Oh, and my Druid Craft is one I am proud of the end result; I encourage you to go ahead and trim it, either way. The cards will look amazingly beautiful.
That was just my humble opinion.