Can an alarplasty/tip-plasty give me a slimmer looking nose and reduce nostril size? (Photo)

Based on your photos, in my experience, you would be expected to do well with a tip rhinoplasty / alar reshaping (with cartilage grafts).  I don't feel you need the dorsal bones worked on.  Be sure to discuss your goals and concerns with your board certified plastic surgeon and consider the pros and the cons. Be certain your surgeon is properly certified.  I've attached a link where you can start your search. 

Hello and thank you for your question. Based on your
photograph, you may benefit from a tip refining rhinoplasty. Your surgeon can
accomplish this by trimming, suturing, and reshaping the cartilage in your
lower nose. You may also benefit from elevating your hanging columella also and addressing the alar retraction.  Make sure you specifically look at before and after
pictures of real patients who have had this surgery performed by your surgeon
and not just a computer animation system. The most important
aspect is to find a surgeon you are comfortable with. I recommend that you seek
consultation with a qualified board-certified plastic surgeon who can evaluate
you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic su

Thank you for your question.  Based on your photos, it appears that you would be a great candidate for tip rhinoplasty to address both tip bulbosity as well as alar-columellar disproportion (which results in your wide nostrils/nostril show).  I recommend that you seek consultation with a rhinoplasty expert to discuss your concerns and determine a surgical plan.  Hope that helps, good luck!