Something like this is always better to use the search function in the forums as there is usually at least one thread about it within the past few months. Since you are new, which its great you are already searching some higher tier items, I would always search for any subject you are curious about, before starting a thread as we generally have multiple already. You have a lot of reading up to do on this subject, there is a lot to learn. There are multiple variants of possible shadowless theme deck variants, base theme decks, but the only way to be 100% sure its shadowless is by it having a gold strip across it.
www.elitefourum.com/t/wotc-shadowless-base-set-theme-decks/16320/1