trouble understanding how to clean up grub for multiboot and multi disk laptop

I have a Dell Inspiron 15 7000, it's a few years old, but works fine still.

It has a 256GB SSD first disk and a 1TB second disk.

I have had several versions of Linux on it over the past few years and also have windows 10. I've been dealing with some weird login menus for a while now and really want to get things cleaned up. Unfortunately, I've been unable to figure out how to do it without risking making my machine unbootable, not enough confidence in the changes.

I went to look at it again today and find even more challenges, for one on the first Linux I tried to look at the drives and the os is only seeing the larger 1TB second drive.

Here is an example of the result:
$ sudo lshw -class disk
*-disk
description: ATA Disk
product: WDC WD10SPZX-75Z
vendor: Western Digital
physical id: 0.0.0
bus info: scsi@1:0.0.0
logical name: /dev/sda
version: 1A01
serial: WX31A878ANT1
size: 931GiB (1TB)
capabilities: gpt-1.00 partitioned partitioned:gpt
configuration: ansiversion=5 guid=ee3471c4-8cc0-4cb7-ae4f-3d0e87e95783 logicalsectorsize=512 sectorsize=4096

I've attached two screenshots, the one with windows is the one that comes up first, selecting ubuntu from that screen takes me to the grub screen next.

Ultimately, here are my goals:

• I want to understand what commands to run to see the partitions on both disk drives and further, to understand how to determine which partitions have which OS's installed.
• I want to understand how to know the impacts of removing what was my first Linux installation and the impact that will have on how the machine will boot.
• I want is to have one boot screen if possible that lists only OSs that are actually installed.
• On the first boot screen, ubuntu, parrot, and windows are listed - parrot is not actually installed any longer and ubuntu actually takes me to the second boot screen. I want this screen to reflect reality.
• On the second screen, ubuntu is listed while it's actually ubuntu studio. This is an old version of it and the partition it's on is too small to upgrade it any further, I want to just remove it.
• All the extra EFI lines, I want to understand what those are, I have no idea. I don't want them listed if they aren't really needed.
• On the second screen, my main everyday use Linux is the Makulu Linux core item, this doesn't reflect that it's been upgraded either, and I'm not clear if I'm actually booting into the newer kernel I have installed - want to understand what's really occurring here.
• On the second screen, there are three ISO's listed, I don't know how those got there, but at one time must have had thumb drives plugged in when running grub update, they still show up even when updating grub without those ISO's being available on a plugged-in thumb drive. I want to clean those up.
• Last, if it's actually possible, I would like to have entries listed for a bunch of different ISO's I have stored on the disk. Is this even possible?

I'm asking for any help you could provide on one or more of these goals. I've been googling and have read dozens of cases, many of which claim to handle some of these, but I get results that don't seem to match what the tools purport to do - I think I'm missing something in my base understanding possibly.
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