Whenever a song starts to get too fast or complicated for me my hands tense up making it even more difficult to play. I've tried different key binds as well as a wrist rest but nothing seems to help.
Don't tense your hands too often (I'm not a doctor, but I'm quite sure there's health issues). You should play beatmaps that aren't too fast or complicated until you can play those harder ones.
Though one time my wrists were in pain, I switched to having my wrists hover while playing and it went completely away, so check your posture as well.
play maps that you’re more comfortable with as this will strengthen your fingers leading to less tensing/strain from your profile you seem relatively new to osu still so you shouldn’t be playing excessively hard maps just yet so stay within a star range you seem to perform well in (95%+ acc) - maybe high 2 star to low 3 star (or higher if you’re comfortable)!
tldr: keep playing more and more as overtime your fingers will become stronger, just stay within a range you’re comfortable in until you feel ready to play slightly harder maps