In the Digimon Card Game, the white archetype of cards has always been relegated to unique and almost off-meta decks, but it has never sustained a real archetype besides D-Reaper. Let's be honest though, D-Reaper is so far detached from traditional Digimon Card Game that at times it feels like D-Reaper is playing a different card game.
Although there are very few white cards in BT10 Xros Encounters, some of them are worth talking about. From meta cards to one-off tech cards for older decks to cards that will be stashed away in the local game store's bulk collection, white cards can be quite interesting when designed correctly.
4 Seiken Meppa
Jesmon GX already feels like a "win more" card, so for Seiken Meppa to unsuspend Jesmon GX and activate its When Digivolving effect just feels like overkill. It is a cool card, and it feels like the stuff you can do with is open to tons of possibilities, like adding another Royal Knight underneath Jesmon, and giving it all sorts of interesting effects.
Sadly, with its cost of three memory, and Jesmon's constant hunger for more memory, the inclusion of this card seems redundant. Especially for a deck that already pushes advantage in the game quickly and with minimal memory usage. Maybe this card will eventually see some play in some rogue decks, or maybe Bandai will introduce a deck solely based on Royal Knights where cards like Seiken Meppa and even Jesmon GX can truly shine.
3 Reinforcement Plug-In 0
Reinforcement Plug-In 0 feels like a card straight out of BT1, where the only thing that matters is who has the biggest DP in the Battle Area. With such a basic effect in "1 of your Digimon gets +3,000 DP until the end of your opponent's turn", this card sticks out of the set as a pretty mediocre card. It's not outright useless. Decks that recycle options, like Sakuyamon, use cards like these quite frequently.
While not as useful as the other Plug-In cards, Plug-In 0's DP increase can come in handy at times when your Sakuyamon might need that extra DP buff, something yellow is not known for, to be able to attack over a big nuisance in the Battle Area. Another downside of this card is that, unlike the other Plug-In cards, if Plug-In 0 is checked in Security, you only gain one memory rather than a search for a Digimon/Tamer or just a draw one. Not necessarily a bad effect, but it doesn't feel as good as the other Plug-In cards.
2 Sistermon Ciel
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Sistermon Ciel is another Sistermon added to the plethora of Sistermon already in Jesmon's arsenal. Jesmon's game plan is quite simple: make a big stack, and play Sistermon for free. Normally, you would want these Sistermon to have different effects, otherwise, the deck would feel redundant and boring to play. This Sistermon Ciel's effect is specifically catered to Jesmon GX — when Jesmon Digivolves, it triggers a myriad of effects. One of them is playing a Sistermon for free.
By playing this Sistermon Ciel, since Jesmon has Blitz, her effect will trigger allowing you to Digivolve mid-attack into the next version of Jesmon. Ideally, you would want to Digivolve into GX — that way, your Jesmon can gain Security Attack +1 for every Royal Knight in its sources. This means adding another Jesmon to play even more Sistermon for free, a Gankoomon X Antibody to give all of your Sistermon protection against effects, or even something out of left field like a Kentaurosmon to prevent your opponent from touching your Security. There are a lot of shenanigans and combo lines with this card alone. While this Sistermon Ciel is not the most important in the deck, it certainly is the most fun to play around with.
1 Omnimon (X Antibody)
There hasn't been a relevant Omnimon deck since the beginning of the game in BT1. Since then, Omnimon cards have been relegated to one-off closers in red or blue decks. With the introduction of this new version of Omnimon (X Antibody), Bandai realized what players are using Omnimon for and just buffed it into the heavens. If Jesmon GX is a "win more" card, then Omnimon (X Antibody) is the card you want to use when you want to morally demolish your opponent.
That's not to say the card is gimmicky. It is quite good and very well-designed. Not only does it send the highest level Digimon to the bottom of the deck, but by it being in the Battle Area, it forces the opponent to deal with it immediately, since its effect lets you look at the opponent's Security cards, pick one, and then trash it.
This effect not only activates when you Digivolve into Omnimon but also when Omnimon attacks. Trashing Security is one of the most powerful effects in Digimon, since trashing the card does not count as checking it, meaning no effects will trigger from that card. Not only is this effect extremely strong, but being able to pick and choose what you trash is downright disrespectful in the best and most fun way possible.