Your predictions about what will happen are hard to answer because [Spoiler](/s "they're kind of a "yes, but not really." Yes there is a school arc, but it's in the middle of the series and it doesn't really have a focus on waifus. This is an arc where the MC establishes many of his friendships and connections that are integral to the story in later arcs. He creates bonds with many people, male and female, who are just friends and not love interests. It's also a part of the series where we get to explore more of the functions of the world as the MC and his friends are doing a lot of research at this time. It's during this arc where you learn a lot of the capabilities and limitations of things like magic. You also learn more about the MC's reincarnation and other important events.
Yes he gets married and has kids, but the harem is limited to only 3 girls and each of them are built up quite well. I'm not a harem person, but this series has what I would call a "harem done right." The girls aren't in love with the MC because he's the MC, they're each given a lot of time to develop their relationships with him. I said in an earlier response that the relationships are done well in this series, this is one of the examples. All the relationships the MC has, with friends, family, and lovers, are done well. They feel like they happen very naturally and aren't forced. And he relies a lot on his friends and family, he leans on them when he's upset or worried or needs advice. The connections the MC makes with other characters are the reason why people praise this series so much because of how well they're implemented.
The MC isn't actually op, or at least not in the sense that you think. While yes he's stronger than your average human, he's nowhere close to being the strongest person in the world. He can win battles that don't actually matter, but whenever he has a battle that does matter he can't do it alone and would die if not for his colleagues helping him out. There's one battle where the MC is literally grovelling in the dirt crying, both arms chopped off, as he begs his opponent to spare his family. He's also held back by very human restraints in battles. MC knows he's powerful and that scares him. He talks about how scared he is that he might kill somebody if he loses control, gets angry, or isn't completely focused on controlling the exact power level of the magic attacks he releases.
MC also doesn't live a fantastic life where he feels happy all of the time. His character is written very realistically where he has worries and fears. He's worried that he's a bad son, a bad brother, a bad husband, a bad father. He thinks about these things a lot because to the MC his family are the most important people in his life. In his old life he treated his family like shit, so he wants to make sure he treasures them and doesn't let them down in this new life. He struggles a lot with the feeling of worthlessness, even into the later volumes.")