My experience with a sixth form that is linked with a school is not too good, mainly because the whole idea of being in sixth form is like entering a maturer stage of life, but when your still at an establishment filled with younger children it kinda ruins that. it can be pretty hard to get around the school when you're path is constantly blocked haha. Another thing which might not be relevant but I've found at my sixth form the teachers find it hard to see us as maturer students as they are used to dealing with younger children and we get treated in the same way.
1) the freedom can be a good thing if you use the time wisely. This can be hard to do but you'll benefit greatly if you use the free time to get work done, just treat free periods like study periods. Also frees can be great when your feeling stressed and just need some time to chill between lessons.
2) kinda answered this above, but a relevant point is that at a sixth form college the teachers have significantly less students most of the time, meaning it is easier for them to keep tabs on how you're achieving. They also have more time to communicate with you.