Good luck writing an interesting story! As for my opinion, I would prefer a setting where the mc doesn't get power-creeped too easily, like the journey is more important than the power up itself. A setting of number 2, with a background of number 3, would be my preferred option in this case, alongside any unique system you can think of would be fine.
Combine 1 and 2. For me, it's easier to write something 'different' instead of writing about established mythos. Cuz then you run into the problem of offending someone's culture or someone's perception of that mythos. HOWEVER...that being said. Do a Danmachi and Fate Stay Night and overturn the pop culture view of those Mythos with Gender bender or some such. That way your readers KNOW's your mythos are 'similar' in some ways. BUT very different in other ways. But that's easier said than done. I'd personally stay with option 1 and 2. Make up a spirit summon system and base the world upon that concept. Best of luck!
I would suggest you Take Spirits and some kind of Sci-fi setting, or at least that´s something i would like to see.
Swords and magic. But I want a complete system if you go level upping. Or simplify them if you focus on story. Don't go to immortal way. Keep mortal.
The stellar spirits you can gain type or the inborn spirit you can nurture type are both good. The catch 'em all type tend to go bad quickly.
There's a wake up in a game world sword novel on here, I cant remember the name. It has a standard leveling system, but his unique class allows him to gain and strengthen cards that can summon, use spells, or boost his sword in some way. Mayne something like that with cards or sentient spirits. An evolving life spirit can be cool too.
If you can't decide between any, choose all three! I don't see how all three ideas can't be in the same universe. Contracted spirits, swords, magic, and mythological gods and demons all seem to fall into the fantasy realm for me. It would be interesting to see how you can incorporate all into the same world and have it be a unique universe!
Why not use demonic spirits? Give it a twist, like spirits are detached bits of the ego of cultivators, no longer necessary, thus discarded to terrorise the lower ranked and inspire them to train or die.