BSF 186 can be used for both goods to accompany and goods to follow. There are options on the form that you can check ( goods to follow Yes or No, in your case, just check No). BSF 186a is simply an extension of BSF 186 to allow you register all your affairs, when you run out of the room on BSF 186. Also, you need to prepare two copies of each forms. One is for CBSA record and one is for your own record.