Trying to understand the flow of images between phone/PC/Mac/iPad

Hello, I've been a happy Lightroom Classic (LRC) user for some time. I'm just starting to get into adding LR Mobile (LRM) to my mix but I'm struggling a bit with what is where an deleting things and Copies vs Virtual Copies.

I'll pick up the Copies/Virtual Copies conundrum later. For now here's where I am at.

I've got an iPhone with LRM on it. I've got an iPad with LRM on it. I've got a Mac Mini with LRM on it. 
And I've got a PC (my main workstation) with LRC on it.

All of the below questions relate to images originating on the iPhone

When I was just using my iPhone to take photos I used to take an image and it would appear in the Camera Roll. iCloud copied that to the Mac, to the iPad, and to the PC.

I could delete an image on the iPhone, on the iPad, on the Mac and it would delete just fine. But if I tried on the PC it would complain.

With a phone upgrade I decided to switch from using Snapseed for editing images that were HEIC and go to LRM/LRC editing DNG files.

I set up the LRM on the iPhone so that Import setting on the app "auto add from camera roll" for photos (not for screenshots or videos).

I've tested and the All Photos view in the iPhone shows all photos whether originating on the iPhone camera (and therefore on Camera Roll) or the Lightroom Camera (and therefore in LRM ony).

I checked on Mac Mini and on iPad and with LRM on those two I can see the same images.

If I DELETE image(s) in LRM on any of those it happily deletes the image(s) on LRM on the other two.

So far so good.

I note that it doesn't delete the images on the Camera Roll though. Which tells me that if I shoot using the main camera (and not the one built in to LRM app) then I get two copies - one in Camera Roll, one in LRM catalog.

That' fine. I can work with that and delete from Camera Roll when I need.

Now for the bit I'm not quite so sure of - the interface to LRC which is on PC in my case.

I've got Sync turned on in LRC. I can see just in the Catalog section an "all synced photographs" item. I can also see in my data drive a folder called "Mobile Downloads.lrdata".

The All Synced Photographs has 154 items in it.

The Mobile Downloads.lrdata has only 78 items in it.

If I hit delete on an item in All Synced Photographs it says "1 photo will be removed from all synced collections and from Lightroom photos on Creative Cloud, but will nto be deleted from the desktop catalog."
If I hit delete when in Mobile Downloads.lrdata folder it says "Remove Photo from Lightroom Catalog. This photo will be removed from your Lightroom Catalog and any synced Lightroom Clients. Select "Delete from Disk" to also move the selected photos on your computer to the Explorer's Recycle Bin."

What I'm trying to achieve is that I go out (today for example I went on a walk in the countryside) and take photos. I download them all to my PC where they are safe and happy and will be backed up by my workstation backup routines, and I can also cull them and delete them as I see fit. Then, *if* I want to share selected images back to my LRM catalogs I can create a Collection and synchronise that collection to the LRM catalogs.

The images might (for example) be the odd snap that I've taken at a wedding that I want to put with the main set of images. Or I might download all images via an SD card reader, whilst at a wedding, and let them sync/backup to the cloud and then download them to my PC and put them where I want on my PC to edit them (removing them from synchronisation on LRM at the same time).

Can anyone tell me how I should be handling images from my phone that are in LRM that I want to get safely into LRC?

At the moment I reckon I'll work it out... but I'd rather do it sooner than later and rather without deleting images I don't mean to delete!

Thanks.