Barebone excel creation + CSV import method. Basis for further work.

New-ExcelDocument.ps1

#region ExcelFunctions

function Get-NormalizedPath ( $Path ) {
    if ( ( Split-Path $Path ) -match '^(\.|)$' ) {
        $Path = Join-Path -Path ( Get-Location ) -ChildPath ( Split-Path -Path $Path -Leaf )
    }
    return $Path
}

$MethodImportCSVtoSheet = {
    Param (
        [string]$Path,
        [string]$SheetName = $null,
        [int]$Sheet = $null
    )
    #
    if ( $Sheet ) { $oSheet = $this.excel.Worksheets.Item($Sheet) }
    else { $oSheet = $this.excel.ActiveSheet }
    $FullPath = Resolve-Path -Path $Path | select -ExpandProperty ProviderPath
    $oSheet.Activate()
    if ( $SheetName ) { $oSheet.Name = $SheetName }
    else { $oSheet.Name = Split-Path -Path $FullPath -Leaf }
    $TxtConnector = ("TEXT;${FullPath}")
    $CellRef = $oSheet.Range('A1')
    $Connector = $oSheet.QueryTables.add($TxtConnector,$CellRef)
    $oSheet.QueryTables.Item($Connector.Name)."TextFileCommaDelimiter" = $True
    $oSheet.QueryTables.Item($Connector.Name).TextFileParseType = 1
    [void] $oSheet.QueryTables.Item($Connector.Name).Refresh()
    [void] $oSheet.QueryTables.Item($Connector.Name).delete()
    $oSheet.Rows.Item(1).Font.Bold = $True
    [void] $oSheet.Rows.Item(1).AutoFilter()
    [void] $oSheet.UsedRange.EntireColumn.AutoFit()
        
    [void] $oSheet.Activate()
    $oSheet.Application.ActiveWindow.SplitRow = 1
    $oSheet.Application.ActiveWindow.FreezePanes = $True
    #>
}

$MethodSaveAs = {
    Param (
        [string]$Path,
        [string]$Format = 51
    )
    $Path = Get-NormalizedPath -Path $Path
    # If ( Test-Path -Path $Path ) { Remove-Item $Path }
    $cachedValue = $this.excel.DisplayAlerts
    $this.excel.DisplayAlerts = $false
    $this.excel.ActiveWorkbook.SaveAs( $Path , $Format )
    $this.excel.DisplayAlerts = $cachedValue
}

$MethodQuit = {
    $this.excel.quit()
    while ( [System.Runtime.Interopservices.Marshal]::ReleaseComObject($this.excel) -gt 0 ) { <#dummy#> }
}

Function New-ExcelDocument {
    [CmdletBinding()]
    Param
    (
        [Parameter()]
        [int]$Sheets = 1,
        [switch]$Visible
    )

    $document = New-Object -TypeName psobject
    Add-Member -InputObject $document -MemberType NoteProperty -Name excel -Value ( New-Object -ComObject excel.application )
    $document.excel.Visible = $Visible
    $cacheSheetsInNewWorkbook = $document.excel.Application.SheetsInNewWorkbook
    $document.excel.Application.SheetsInNewWorkbook = 1
    [void] $document.excel.Workbooks.Add()
    $document.excel.Application.SheetsInNewWorkbook = $cacheSheetsInNewWorkbook
    Add-Member -InputObject $document -MemberType ScriptMethod -Name ImportCSV -Value $MethodImportCSVtoSheet
    Add-Member -InputObject $document -MemberType ScriptMethod -Name SaveAs -Value $MethodSaveAs
    Add-Member -InputObject $document -MemberType ScriptMethod -Name Quit -Value $MethodQuit
    return $document
}

#endregion

$test = New-ExcelDocument -Sheets 1 -Visible
$test.ImportCSV('test.csv','testouille')
$test.SaveAs('test.xlsx')
$test.Quit()