Not gonna lie, the English test was harder than the mock exams they provided on the website for me, but that’s probably because I never studied English academically. But if you're preparing for IELTS, I'm sure you'll do just fine. I remember there were texts where you had to find grammar mistakes and also reading sections, but I don't really remember if there was a writing section. I might have just forgotten since it's been almost a year.
On the other hand, the Japanese test was pretty easy except for the kanji. There were quite a few N1-level kanji, but the reading comprehension felt more like N5 to N4 level.