Cursor left / right in horizontal surround, by default, moves word-by-word, however, you can use Shift + Left/Right to move character by character for fine tuning.
However, it would be easier to use if the logic for this were a bit smarter. I'll tweak the code to have it recognize parens and identifiers and numbers rather than just leaning on next-word/prev-word like it does. This will be in the next hot fix or 27.0.1, whichever comes first.
