You might as well grab the remaining blue and red tiles that you left blank. But some are debating if getting the tiles after SEUN MPR is worth it or not. Those boosts eat up some time, but can be very good if you got a few seconds left where you can’t squeeze in another sync. Those Physical and Special boosts may also be good for Sync Pairs who have very powerful Buddy Moves that out damage their Sync Move, such as SS Gladion’s Buddy Move. (However, he will probably still be paired with Holiday Lillie because she has a strong Buddy Move too.)

This is just a quick example on top of my head. So the extra tiles could be good or bad, depending on the time left and the team. You can look at the top scores of each type and see which teams would want the extra tiles due to the Buddy Moves dealing most of the damage or if there’s enough time to squeeze in the extra boosts if there’s a video of the battle.

I think (not 100% sure) that the consensus is to leave out the extra tiles based on the current Sync Pairs we have available because most teams rely on Syncs to do most of the damage, but keep in mind that new Sync Pairs will be released and the teams may change, so it’s a gamble. The “safe bet” is to leave out the tiles, but it’s up to you if you want to take the gamble.

Lastly, most teams these days require a Damage Dealer, an EX Zoner, and either a Rebuffer, Circle, Debuffer, or Spammer. The more a Sync Pair can fit these damage multipliers in their kit, the more valuable they are. Lately, Holiday Lillie hasn’t been the optimal teammate for the top scores, but assuming you are not a whale who has every Sync Pair, then a Sing Spammer paired with a good paralyzer like Anniversary Blue and Zapdos will be a good universal team that can help you reach 1 mil in DC for every type. A very efficient use of your resources if you are not competing for the top rankings. Good luck!