Thinking to get invisalign for crossbite, will it make my jaw/chin smaller?

Depends on crossbite: You have not designated what type of crossbite you have. If it is on the back teeth, then its correction will have little impact on your profile. If it is an anterior crossbite, and your lower jaw has been posturing forward to avoid front tooth interferences, then correction may result in a reposturing of the lower jaw backward, which could result in a mild reduction in the prominence of your chin.

Should not: If done properly, it will only give you a beautiful smile!

Teeth will look diff: If you have a crossbite in the front, the treatment will move your front teeth forward over your lower teeth ( hopefully) and will certainly make your smile wider in the front. I doubt that it will change the shape or the anatomy of your chin.

Smaller chin: No. Any type of braces will not make your chin smaller. However, it will cause your lower jaw to drop downward and backward thus giving you an apparent smaller chin point. Often, this might not be that noticeable, and in time, growth may recover the apparent loss of chin point.

NO: Invisalign treatment will not affect chin/jaw size.

Unlikely: Invisalign is wonderful, but it may not be able to generate enough force to influence the size of your jaw or chin.

No: Clear aligners are on average 41% effective at aligning teeth! braces are 95% effective! but neither changes jaw relationships in non-growing adults. If i'm reading your question correctly you need the services of 2 specialists, an orthodontist and an oral surgeon. Aligners won't do it. Talk to an orthodontiist about extent of your problem and available treatment options.

Wrong treatment type: Invisalign is NOT the treatment of choice to correct a crossbite. I presume since you mention having a prominent chin that you have an anterior crossbite. In adults it usually requires a combination of braces and oral surgery to correct this condition as it is too late to redirect growth as the jaw bones are done growing. An orthodontist can help guide you to proper treatment options.

No: No. Chin and jaw will remain the same.

No: Consider traditional braces for most exceptional correction of crossbite. See an Orthodontist, not someone who "does invisalign" or also "does invisalign". You need the complete diagnosis done by a specialist before moving ahead. Good Luck.