How Do I Set Up iCloud So That I Don’t Accidentally Overwrite Text Documents?

I’m a student who writes a lot of papers. I write primarily on Scrivener, Pages, and Microsoft Word. I’ve recently switched to a Mac and I’ve been thinking about turning on iCloud, for the convenience and peace of mind of having a backup. But I’m reluctant to do it, because I don’t fully understand how the syncing works, despite watching a number of online tutorials, including those on Macmost. I’m worried that I might accidentally lose or overwrite hours of my work by accidentally syncing together conflicting versions of the same file. I’m wondering if there is a way to make sure that this doesn’t happen.
Here are a few further details about my situation. I don’t always have an internet connection: sometimes I work outdoors or in restaurants or cafes without any wireless service. For that reason, I have decided that I want to keep all of my iCloud document files local on my Mac (by turning off “Optimize storage”, as the Macmost tutorial says). In that case, however, it’s possible that I will have worked on a file for several hours (if not more) before I get internet connection again and can send the edits to iCloud. Is there any risk that, if I accidentally do something on another device before my offline changes have gone through, that my offline work will be lost once I get my connection back, and the different versions of the file get synced?
And finally, I don’t always work on my mac but also on other apple devices (an iPad and an iPhone) and on library computers (Mac and PC). Are there any syncing problems that can arise–specifically in text documents (.docx,.pages,.scriv)–from working on a file across multiple machines like this, sometimes offline and sometimes not?
I’d like to be able to have a running cloud back up of my written work, so that I am less likely to lose it and so that I can back up my work whenever I have an internet connection. (At home I use external hard drives to back up my work, but I do not take them with me when I leave the house.) However, I do not want to use an online back up service like iCloud without understanding it, because if I do I might accidentally wipe out large sections of a document that I spent hours of time working on. That’s why I’m asking: I’d like to know how to set up my iCloud backup in such a way as to avoid losing work through improper syncing.
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Balon K.