If you are getting a K1, you cannot marry in Canada, you have to wait until you have the visa and then get married in the US.
No, if you marry in Canada, you cannot then just go to the US and apply to adjust status. It is not that easy.
Stay away from those visa kit sites, they're rubbish, and there is no need to pay for the forms. All the forms are available for FREE on the USCIS website, and all the information you are ever going to need during the process is available for FREE on Visa Journey


