Niagara couldn't be a t5 its smaller than a galaxy class, it would make a good t3 cruiser.

Raging Queen and Curry-Type are kit-bashes of the excelsior class so they are tiny as well.

The Excelsior class was considered to be one of the most successful designs after the failed "transwarp" was replaced with a standard FTL drive and that ship was seen on screen more times than any other ship (Hero ships not included).

I don't know if you are quoting from the TNG technical guide but it isn't considered canon and a lot of the information in it isn't accurate.

And that website isnt a good source, try Memory Alpha, the Star Trek Wiki and Ex Astris Scientia