I find this Tim Horton's in T1 F gates to be much busier than the Timmy's at D gates just after security.
There is really not enough seating both inside and outside of this restaurant. This place is tight, people have hand carry and other type of bags/luggage and there's hardly any room to move inside .
The food is the same at any Tim's. They have a full stock of all doughnuts first thing in the morning and all sandwiches etc. The line ups seem to move pretty fast though and they do have a dedicated line for drinks for morning hours.