New SSD won't allow my to install old OSX

Hi there,

I have a mid 2014 macbook pro that I've replaced the SSD on today (OWC Aura SSD upgrade kit). (reason in previous post: Should I replace the hard drive if my Mac… - Apple Community)

When I started it in recovery it encouraged me to install big sur so I went ahead with it and all seemed fine.

What I actually want on there is high sierra so I can use old software (I realise most people wouldn't waste time on an old computer or an old osx but I have my reasons and I also have a 2024 macbook pro as my main computer fyi).

I am struggling to make a bootable usb with high sierra on - I follow tutorials but it never works. But I have Mojave on a USB so I installed that and again it seemed fine, then I went to sign in and then the screen went black with some sort of error sign (circle with a cross through it).

What am I asking?!

1. what could be the reason for this error?
2. if mojave won't install correctly will it likely be the same for high sierra
3. what's the simplest way to make a bootable usb of high sierra (tried using terminal and always fails)
4. if I end up just wanting to resell the new SSD (as used) I bought do I just open disk utility and erase to format it fully? (there are no files on there, just literally my attempts to install osx and my new profile)

As you can tell I don't totally know what I'm doing so any kind guidance would be gratefully received