Dual Boot permissions

The first half of this question is more about Dual Boot than OCLP to be honest. But...

Last week I copied my SSD onto a new, larger SSD using CCC. Mid-2012 MBP, running Catalina. Then, after putting the new SSD in as the internal drive, I created a new volume on the disk, and onto that volume I installed the latest Sequoia version using OCLP. All working very nicely, mostly!

So now I have a couple of harddrive images on the desktop - the "New SSD" volume (Sequoia) and the old "Macintosh SSD" (actually I also have a third because the first time I tried installing Sequoia it created the Data volume and installed Sequoia onto that). So far, as expected. What I hadn't expected, however, is that while booted into Sequoia I am able to click into my old SSD image and access all files without having to enter a password. Not a massive problem, but it does seem strange that I can just go into a separate boot drive from another bypassing the password for that other bootdrive, and I'd like to at least understand why.

As a perhaps more OCLP-related question - if I put the "New SSD" drive image into the very top right corner of the desktop, when I restart and log back in, it's moved itself down a space and the first 'space' in the grid is left blank. Then when I, say, take a screenshot, or connect an external drive, those screenshots/drives are all added to the same very top far right space of the desktop on top of each other, which is a bit annoying. Not sure how to stop it doing that (without using Stacks). Is this an OCLP quirk or is there some other setting I've forgotten about...