The graphics artifacts are usually a sign that your manufacturer is currently using a broken Android 13 revision. You can try enabling ANGLE in developer options - see https://github.com/ppy/osu/issues/25189#issuecomment-1832176491 - but if that doesn't work, all you can do is wait for the manufacturer to ship the fix.
As for the "laging," the mobile builds are provided as is for now and no serious performance work has been done for them. Desktop takes priority.
