Isekai Tensei ni Kansha wo
This is a warmhearted isekai where an elderly gamer with diabetes and other health problems gets reincarnated while playing a full-dive VR game. In his new youthful body, he sets out to be an adventurer using the skills he purchased at the beginning of the game. In the process, his kind and wise nature draws in a lot of people and eventually results in his first romantic relationships in his life.
Overall, this story is easygoing and warm-hearted from beginning to end. A large reason for this is that the setting is one where the constant threat of monsters and the lesson of how monsters destroyed civilization when people got obsessed with fighting each other has pretty much ended nation vs nation warfare. For those with a fondness for fantasy adventure but don't want the political conflicts that are usually endemic to isekai, this is actually a pretty decent choice. The protagonist himself is a gentle and wise man, while having the strength of will to do what is necessary.
Fukushuu wa Tenbatsu o Yobi, Majutsushi wa Poyapoya o Tanoshimitai
This one is a bit of an oddball series. In this case, the protagonist, who just took revenge for his wife and daughter's death at the hands of a rich boy's hit and run, is about to turn himself into the police when a meteor falls on his head. His soul is ripped from his body and forced through the void, gaining power along the way until it accidentally enters the soulless body of a dying young boy named Ricardo.
A lot of this story is about the protagonist pursuing various lines of sorcerous research and teaching others with short periods of intense action. The protagonist was a teacher in his previous life, so he has a good deal of general knowledge (better than the average isekai protagonist) as well as the advantage of a growth ability that other people can't access. Throughout the first two-thirds of the story, I wouldn't call him overpowered, though some of the devices he develops are. However, late into the story he basically stops being on a human level and becomes more powerful than the rest of the human race.
There is mild romance (slow-burn romance with a younger woman), nepotism (the businesses he starts are mostly dropped in his family's hands), and lots of obsessive research into magic and magic devices.
All in all, it is a pretty balanced story, with no single aspect being given too much time. There are a few points where the story slows, but those periods are relatively rare (compared to other isekai that get over 100 chapters).
Kurono Senki, Isekai Ten'i shita Boku ga Saikyou nano wa Bed no Ue Dake no you desu
This one never got completed, so don't take this as a recommendation for it. Sadly, I can see why the author dropped it toward the end, as it drags on and there is a lot less insight into characters and character motivations as things go on, making it obvious he was just putting one foot in front of the other for large periods of the story.
Kurono, the protagonist, is a young man who gets transferred to another world that is full of war and is taken in by a former mercenary turned aristocrat with a military bent. Kurono himself has no real talent for the military, but he has the usual wide and shallow spread of modern knowledge from his high school education. At the beginning of the story, he fights a desperate battle after his superior ran off and left him in charge of the demi-human soldiers (who are considered disposable). He manages to achieve a costly victory and as a result becomes a noble in his own right, where he starts making reforms based on his knowledge of Earth.
He also takes a LOT of mistresses along the way, most of them elves and half-elves who were abused earlier in life. His taste for women only gets stronger as the story goes by, and it is probably the reason for the weird title. I will say that the periods where the action intensifies are first-rate, but the periods in between drag on for what feels like forever. There is far too much time spent on other perspectives and his sex life (I won't call it romance, because the only ones he seems to truly love from his heart are Layla the half-elf and the elf twins).
Overall, it is an interesting story that never really lives up to its potential because the author kept losing motivation in the middle.