Fast filtering after Get-ChildItem - regex

Question

With PowerShell 5.1 and the new .NET framework, it is finally possible to work with long path names using Get-ChildItem -Path "\\?\C:\MyPath".
In the code below we try to filter out files and folders that are in specific directories (as well as the directories themselves), because we're not interested in them.
This code works fine, but we were wondering if there is a better or faster way of doing this instead of building a long regex string?
In case the array $IgnoredFolders gets really long, it might take more time for -notmatch to make the decision. I'm not an expert in regex and how long they may become, so any feedback is welcome.
<#
# Path
Folder A
File folder A.txt
Folder B
File folder B.txt
Folder C
File folder C.txt
File root A.txt
File root B.txt
#>
$Path = 'S:\testFolder'
$IgnoredFolders = #(
"$Path\Folder B"
"$Path\Folder C"
)
$RegexIgnoredFolders = $IgnoredFolders.ForEach({
[Regex]::Escape("\\?\$_")
}) -join '|'
#(Get-ChildItem -LiteralPath "\\?\$Path" -Recurse).Where({
$_.FullName -notmatch $RegexIgnoredFolders
}) | select fullname
The output of this code is:
"$Path\Folder A"
"$Path\File root A.txt"
"$Path\File root B.txt"
"$Path\Folder A\File folder A.txt"