In general this is not a very common construction in everyday French, it is rather literary.
Ne le savoir que trop (bien is optional and not very common) is an exception, it's a bit of an idiom. The Trésor de la langue française has an entry for ne le savoir que trop — two, actually, one that it defines as “having had the bitter experience” and one for which it gives a more general meaning that simply reinforces “I know”. Indeed this expression can be used even by someone who hasn't had the direct experience, although it might be considered an exaggeration in this case.
In general, I think that because this construction (ne … que + adjective) indicates emphasis, it's natural to combine it with a superlative, unless the adjective is already a comparative. (A superlative comparative is possible in French — “beaucoup plus grand” — but it feels too much here.) Trop is not the only possibility, straight superlative marker such as bien, fort and très (the normal superlative marker in modern French) are also possible, but rarer. The comparative is the most common case, I think. This includes ne … que plus … and irregular forms of comparative such as ne … que mieux, but also semantic comparatives expressed with a verb.
On peut juger Delacroix d'après les feuillets de son Journal : il n'en sortira que grandi. Auteur non déterminé, in Revue politique et littéraire, vol. 50, p. 360, 1912
I can't find either a quote or a sentence I would naturally write that wouldn't have either a comparative or a superlative.