My optician said strabismus surgery isn t worth the risk, as it may do more harm than good. Is this true? My eye wanders quite noticeably sometimes

Consider the source. I would consult with one or more ophthalmologists who has completed the extra surgical fellowship training & done if for years.With that level of training & experience you can expect the doc to have handled cases similar to yours & be up to date on new methods of treatment.Accepting random observations by someone not trained in the area could prevent you from achieving your goals.
No. Depends on a lot of factors -- see a strabismus surgeon (peds ophtho) before concluding that if your vision is good and it doesn't bother you that it much, it may be more cosmetic.