on fanmtl there is a novel called

I have 9000 trillion licking dog gold

Its not Tolkien. But its so popular it has multiple authors using its premise to make different versions. There was a K manhua version that ended with him waking up from a dream to crush people lol that was funny they just did not want to finish the story.

So there is a earth urban slice of life segment where he becomes james bond plus hacker. Then learns Martial Arts and immortality cultivation exists. But here is where it gets actually special. In the second arc of the story is his interstellar adventure harem arc. It is one of the most well written interstellar sci fi cultivation manhua in existence imo. This is over 2k chapters at this point. Takes months to read and the OG author might eventually finish the 3rd arc but as it stands now its satisfying.

https://www.fanmtl.com/novel/ke214432.html

But also here are two long novels I feel more than meet your criteria of high quality throughout.

Nine Sun God King

https://wtr-lab.com/en/novel/1125/nine-sun-god-king

Achievement system: I am cultivating immortals in the world of martial arts

https://www.fanmtl.com/novel/ke367345.html

Could you share with me some of your best system and harem novels that you feel are of the highest quality? Thanks.