I guess to me, your threading needles. The cache from what you and I are saying, are the same thing:a file or files that an application will build and use to allow things to be accessed quicker. Whether it is an incremental(part) or initial(full), they will still work together, though in different ways. One is a full, and the other is an ongoing. It is pretty much the way backups work with servers(minus the bit being reset in a way) and also within the registry of computers. But that is going much deeper than this discussion to a large extent is needed by a beginner and probably would, from what u have been reading, turn them off.
I will go a bit further and elaborate that going not only from one rom to another can cause potential problems, but, from one version to another of an application, as the way a code is written can store different language hooks, which may or may not be the same, or written differently in different versions. You do not have to do it (wiping the davlik or regular cache), but it is better to do so, and can avoid many problems. Not to mention, it is better to just get in the habit of doing so.
The same goes for the system wipes. I mean, let's be honest here, you, I and many others are so into this and other things that they overlap one another. That being said, 90% of what we are debating is going to go over the average users head( no insult to anyone's knowledge or lack there of, myself included as the is always something to learn), so saying that "you should do it because it's easy and it can avoid problems", is probably all they want to know when first starting out. I know I did.
I was afraid to do it, and just didn't want to break my phone. So a lot of the technical came later (over the past month or so with reading and messing around), after the initial and successful root and then rom install.
Breaking down the components is not for everyone, just like I have realized rooting and roming isn't. Yes, better to know, but depending on the method (especially twrp), sincerely not necessary at first.
Maybe I misunderstood something. If so, apologies.
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