1) 10k - The most I see myself doing eventually. Offers the most room from creativity
2) 8k - Currently training to play 8k better. 8k patterns are noticeably different from 7k ones due to people from BMS primarilty mapping them.
3) 6k - I like even number of keys, and 6k offers something in between 4k and 7k which I will explain in the following
4) 7k - Offers more room for patterns, but I am just not a fan of odd number keys. I like to use the same number of keys on either hand.
5) 4k - There is a point in 4k, above 5.0 stars, which makes you question what the hell you are playing. This keymode at the end of the day is nothing more than stamina and speed. Any flexibilty higher keymodes may provide is comparable to inverted maps in this keymode, which is the only other type of reasonable difficulty in this.
6) 5k - I don't know what your key setups for 5k are, but I play (123 numpad8 numpad9), and I really got used to that to a point that using anything else feels weird. However, it puts a lot of strain on my left hand. Also I am not entirely sure why, but 5k seems harder for my than 7k despite me using same fingers+2 more. Just not my cup of tea
7) 9k - As you already know, I have a thing against odd numbered keyed maps. It also doesn't help that my brain thinks 9k is either 8k or 10k when trying to play. 7k is still fine since the thumbs can be independently controlled pretty well, but I choke on the pinky.
8) 1k - Jack-ass jackmode is the only way to describe this
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12-18k - I can do up to 2.7* auto converts on 14k, but that's pretty much it. It requires me to use 2 keyboards to avoid ghosting issues. This has no rank, it's just outside the scope where I don't even know what to give this.
2-3k - 2k is a nice way to practice the standard mode tapping (which I really suck at) and 3k is great for drumming/Synth maps. That's pretty much it.