Side Decking at the Beginning of the Format

It's going to be basically the same as last format.

The main difference is that you would shift the attention that would have gone to siding against (Quickdraw) Plants to siding against X-Sabers. Dandylion getting Limited essentially killed (Quickdraw) Plants, and the TCG doesn't have T.G. Hyper Librarian yet, so Junk Doppel isn't viable.

X-Sabers may have lost some of their defensive capabilities in losing two Book of Moon and one Solemn Warning, but those limits also benefit them. Trap Stun is much more effective with less Quick-Play Spells that can be used to render it useless. So, the Boggart Knight-Pashuul-Faultroll-Hyunlei play is much safer and can give more advantage.

As always, Effect Veiler can save you in that situation. But, let's not forget about Forbidden Chalice. Setting it makes it look like you could have a Counter Trap that your opponent would want to pre-emptively Trap Stun. Then, you could Chain it to Boggart Knight's effect, and it would be useless. Or, if they already had the materials for Hyunlei out and it was your only back row, you can Chain it to Hyunlei's effect, targeting Faultroll.

An interesting Side Deck option that I would like to bring to your attention in this match-up is Synchro Control. You can't really use it all that effectively if you're going to be spamming Synchros yourself, but it can be quite helpful in the X-Saber match-up, and in other match-ups as well. Being a Quick-Play allows you to play it through Trap Stun, and it also lets you keep the Synchro Monster until the end of your turn, even if you take it on the opponent's turn.

The best thing to do with a XX-Saber Gottoms stolen this way would be to attack, then tribute it to rip a card out of your opponent's hand. If you weren't so fortunate and could only steal a Hyunlei, then you should make sure you tribute it, Synchro with it, or push for game before they get it back.

If you couldn't tell already, I'm mainly advocating Quick-Play Spells because Trap Stun is going to be a lot more popular, not only in X-Sabers, but also in Gladiator Beasts. However, all of these Quick-Play Spells could be stopped by Forbidden Lance, which is also gaining popularity. If you still fear the threat of Forbidden Lance, then just use Effect Veiler.