Hey
I used to play with a mouse (1500 dpi, default windows and ingame sens) for about a year before I switched to a tablet.
I got used to it in like 2 days or something (plus I immediately saw some good results)
It just takes some practice (and experience in the game to make the transition easier imo)
And as others said, it's like relearning the game so play with some lower difficulties to get used to the tablet. Playing full area is like playing with a low dpi imo (you have to move your whole arm just like on a low dpi mouse)
Also I recommend finding the right settings for you (osu resolution. active area, etc) and get used to it/practice a lot with it
Enjoy your tab