But being a linguist of sorts with fake languages is a good way to become a good real linguist, even if only of the hobby variety. So, in that direction, it is important to be clear about a number of distinctions (and, alas, some of the technical terms that go with them). First there the branches of linguistics: phonology (sounds and how they go together to form phonemes), morphology (meaningful strings of sound and how they go together to form morphemes and these go together to form words), syntax (how words go together to form sentences -- and intermediate phrases along the way), semantics (the meaning of morphemes and how these interact to give meaning to all the structures up though sentences -- and beyond), pragmatics (tying that meaning into the context of utterance), rhetoric (dealing with the emotional and social aspects of the sentence -- this sometimes folded into pragmatics, and, indeed all these divisions are somewhat arbitrary in particular cases).
So, in particular, every language has a morphology. Languages range from the totally isolating type, where every morpheme is free, a word in itself, to the polysynthetic, where every morpheme is bound and words are always complex -- with various stops in between.
"periphrasis" is a word in comparative linguistics: what one language does within a word, another does using two or more words. Of course, this assumes that we can identify "what a language does" and this usually turns out to be a semantic category of some sort (or a pragmatic one). It may be the case that the two languages really are doing "the same thing" in different ways, bt it generally turns out that they are doing slightly (or grossly) different things which can sometimes be substituted for one another. tp is a totally isolating language, so, inevitably, if it does something like watt some language does with cases or tenses or whatever, it does it periphrastically. But there is no a priori reason to think that tp does do the same thing as some other language.
Subject and Object and Agent and Patient are pairs of categories from two different fields (syntax and semantics), but they are highly coordinated in many (most? all?) languages, though they may mean somewhat different things in each. So it is important to keep them separated to be clear what you are saying. Thus, the whole talk about the order of agents and patients, is misleading, since semantic categories are nonlinear for the most part, If we keep that in mind, of course, then the talk about the order of the categories can be understood as shorthand for the order of the words that bear these categories. But it is nice to know that the person doing the shorthand is aware that he is doing so.