Confused on 265/65R17 Tires

OK reading through all the threads on the Billie 5100's everyone keeps saying that these are only used as a means of leveling which ok I understand and then people ask if they can fit 285's and the answer pretty much is no. Here's my confusion (which may be lack of tire knowledge) Everyone keeps saying the max you can pretty much go is 265/70..i bought my truck and its has some Dunlop street tire that are 265/65R17 from the looks of it I could easily fit 275's..long story short do different 265's have actual different heights/widths depending on A/T or MT or brands?
Thanks and again sorry for the inexperienced question

 

Yes they can vary from tire to tire based of tread.

 

While the wheel well looks quite large with stock tires, anything over a 265/70-17 will probably rub at full lock. This is where trimming is required. To be honest with you I have a set of Yokohama HT-Ss in 265-70-17 on mine with a 3/4" spacer and it rubs on one side at full lock.