I honestly think that positioning plays a big part in how well you can do in certain skill-oriented high-speed games like osu!. This may not apply to everyone, but if you find that you're having trouble after rearranging some stuff, then it could be the case for you.
Basically, as soon as I noticed that this was a thing for me, I try my hardest to realize all the little specifics in the way that I sit, the position of my mouse/keyboard, where my arm is, etc. For you, it would've been better if you paid more attention to these things before you got your new setup, but I guess the best thing to do now is to just try to find a new position that you're most comfortable with playing in, and memorize that position very well.
Of course, this makes you less inclined to adjust your position or playing style if someone tells you there's a better way to do it, but I think it's still useful for playing more consistently.