When you press X, it INSTANTLY skips to the end of the current textbox. Same with holding C, it doesn't go through each of the letters but instead progresses past through each textbox quickly. So, essentially, language setting doesn't make a difference. It MIGHT make a difference on the "Susie joined the team!" textbox and the textbox after that one ("Susie followed at a distance as to not be associated!") but it probably doesn't due to the fanfare.
It actually does. Check this thread https://www.speedrun.com/deltarune/thread/9utuj
At the start (before Toriel speaks) there is less text in every text box in the Japanese version so you can get through text boxes quicker than the English ones.
About a month ago, there was a community poll held in the discord to add IGT to Deltarune. After a close poll of about 70 to 5, we have added the use of IGT to the game. This IGT only makes a difference to the All Chapters categories, removing the time spent switching between chapter 1 and chapter 2
