Installing Ventoy in USB for multiple troubleshooting .ISO apps

Hello,

I've been trying to install Ventoy into my new 3.0 64GB USB thumbdrives and it's not working so far, by following the Ventoy site's instructions. I mainly want to install the Windows 10 .ISO using the Windows Media Creation Tool and Hiren's Boot CD for now.

First, I need to understand a few things and how to check what's in a USB set up for this. Questions:
1- If I download an ISO file to my local drive through File Explorer, I can see a single ISO file where I downloaded it to. I understand "mount" to mean the ISO file opens to reveal the folders and files of the ISO, sort of like when a zip file extracts, it just extracts the files and folders but they don't run until you want a file to run. Is this correct?
2- If 1 is correct, what am I supposed to see in the Ventoy USB drive with the ISOs in it using File Explorer, - just ISO files or folders and files?
3- When the Ventoy USB is all set up with the ISO files in it, what happens when the USB thumbdrive is plugged into the PC, especially if the PC won't fully boot up - does it autorun something or do I have to find what I need and run that manually?

When I'm clear/learn about the above, I can probably explain my Ventoy install fails better.

Please advise.

Thank you

Just an FYI - on my system, I've found that booting without Secure Boot and in exFAT seems to work best.

Regardless, remember that you can change most of the options (including upgrading to a newer version) without effecting your ISOs.

Thanks for the replies. I sort of get it now. Once I get it working I'll understand it more.

Now I'll try to install Ventoy again. What isn't clear in their install instructions is whether it matters what version of Windows the ISOs are intended to work with. For example, as I understand it the Ventoy pre-install window offers options of MBR and GPT and also what to pre-format the USB stick to (I understand an SD card in a USB card adapter function the same). When Ventoy installs, it wipes whatever is on the USB stick and I think formats it too. Correct? Another thing is the version of Windows v1703 and whether it's a pre (Legacy MBR) or post v1703 UEFI.

So, what do I need to pre-format the USB stick to, FAT32? What does Ventoy format it to? Does it matter If I select MBR or GPT for either a pre or post Windows v1703? I've tried the Ventoy install with every combination and they've all failed. I also tried their LiveCD workaround with Rufus and that also failed on new and known good USB drives. I must be missing some step for the install. What's your step by step install recommendation?