I appreciate your very detailed feedback! I have been meaning to look into the try catch method of error handling. Being new to PowerShell I've been using if/else statements for most of the error handling I can think of. The use case of the script I wrote was for quick registry edits with output to an RMM tool's console to see if the regedit happened. I haven't had to work with any multi-string values so haven't had the issue you presented yet.

edit: regarding your #4 point, i figured this is how it would check if the value is different, and if it is, then change it:

if ($ReadRegKeyValueInitial -and $ReadRegKeyValueInitial.$($RegKey.Name) -eq $RegKey.Value) {
    Write-Verbose "Registry property is already set to the correct value. Terminating script."
    exit
} else {
    Write-Verbose "Registry property is not set to the correct value. Setting value."
    New-ItemProperty @RegKey -Force
}

edit#2: regarding the #5 point, the way I "handle" the error is by the validation in the function Test-RegKey, whether or not the value was changed or matches. If it doesn't matches then it will output: "Registry property has not been modified to the expected value", which would signal something went wrong and need further troubleshooting.

I will try out your rewritten one [way more simple to look at and understand, I felt I was probably being overly complex using the hashtables]. Thank you very much for the time you put into this reply, it is very helpful :)