> 1. Separable verbs in German. My favourite example is "Ich bringe meine Frau (um)". "Umbringen" means "to kill". "Bringen" means, well, "to bring". So you can't start translating German to English until you hear the whole sentence a lot of the time. I believe this has a name in linguistics. Front loading of information? Something like that?
Well, but you can often translate incomplete German sentences to another SOV language easily.
> 2. Word order. Again in German, "Ich habe meine Frau gebraucht" (I brought my wife). You don't know the verb until the end. For reference, the kill version is the fairly sane "umgebraucht".
Well, it's just a different mental model of incomplete sentences / information. With SOV word order you just infer that the S and O have a relationship and make the nature of the relationship more precise after.
> 3. Many Indo-European languages have strict requirements where words have to agree in case, gender, number and even article (eg in German this changes based on the definite vs the indefinite article). I have trouble believing this doesn't have a cognitive load. This does allow shortcuts. For example, it seems like it's common to omit the subject pronoun because when it's obvious from the verb conjugation.
As you mention, what complex morphology gives can allow someone to waive finding a precise word in a language without that morphology. It's not like these distinctions don't add information on their own, however arbitrary they are.
> 3. Writing system.
I agree that Chinese character-based scripts cognitively heavy, but this is a characteristic of the script, not the language.
> 4. Suffixes to change word meaning also mean you need to keep that word in mind until you hear the end of it. Word order just seems so much more predictable but that could definitely be native English bias.
write vs. writing, writer, rightly, etc.
turn up, turnaround, turner, etc.
There's more nuance to what where these counterpoints are coming from, but I think I've given some food for thought. The points you mention look to me very typical of someone learning a more inflected language.
But consider also the flipside of learning Classical Chinese, which fails to make many distinctions that many languages make. You might, say, struggle with the ambiguity: is the action meant to be in the present, past or future? But perhaps that is not important with respect to the passage (and the language has tools to signify it where important). And consider also that in languages like English where tense needs to be signified, in narrative contexts where tense is not important, we conventionally use the past, but may use the present (historic present) for stylistic effect.
Note on Classical Chinese: of course, it survives only in writing, and beyond Old Chinese it is a separate language from the vernacular, and it is not very friendly to being spoken in the pronunciation of in the modern Chinese languages. But books like the Mencius were dialogues that presumably recorded Old Chinese.