There are so many different ways to accomplish these goals of yours. Here's one:

You mentioned that you don't like recreating instances of WebView... I concur. I localized both WebView , and WebPage into ContentView. WebView stays in the body, and I call .load() on WebPage when a new Tab is selected. It's been a while since I used TabView for anything.

It seems like there might be a .init ( selection:Binding < Hashable >) to call, but all I saw were Tab's that required the setting of a new View with each instance. Not very appropriate when we want to maintain a single View and load new Data. Maybe I missed something. There's probably a new modifier? I changed Color.red to EmptyView(), and set a frame or two.

I wish I could tell you more about the performance issues you mentioned. Maybe someone more qualified could speak to that. I don't see much issue.

Tested and working on macOS 26 & #Previews iPhone 16e , iOS 26.
Here's your code back.

enum Tabs: String , Hashable , CaseIterable  {
    case home , cnn , fox , msnbc
    var url: URL? {
        switch self {
            case .home  : URL ( string: "https://www.stackoverflow.com" )
            case .cnn   : URL ( string: "https://www.cnn.com"                   )
            case .fox   : URL ( string: "https://www.foxnews.com"           )
            case .msnbc : URL ( string: "https://www.msnbc.com"                 )
        }
    }
    var label: Label < Text , Image > {
        switch self {
            case .home  : Label ( "Home"  , systemImage: "house"     )
            case .cnn       : Label ( "CNN"   , systemImage: "tv"            )
            case .fox       : Label ( "FOX"   , systemImage: "newspaper" )
            case .msnbc : Label ( "MSNBC" , systemImage: "paperclip" )
        }
    }
//  var tab: Tab < Tabs , EmptyView ,  Label < Text , Image > > {
//      Tab ( value: self , content: { EmptyView() } , label: { self.label } )
//  }
}

@available( iOS 26.0 , macOS 26.0 , * )
struct ContentView: View {
    @State private var selectedTab: Tabs = .home
    @State private var webPage: WebPage = .init()
    private static var macOSIgnoresSafeArea: Edge.Set {
        #if os( macOS )
        .top #else
        [ ] #endif
    }
    var body: some View {
        VStack {
            WebView ( self.webPage )
                .edgesIgnoringSafeArea ( Self.macOSIgnoresSafeArea )
            TabView ( selection: self.$selectedTab ) {
                ForEach ( Tabs.allCases , id: \.self ) { tab in
                    Tab ( value: tab , content: { EmptyView() } , label: { tab.label } )
                }
            }
            .frame ( height: 50 )
        }
        .task ( id: self.selectedTab ) { self.webPage.load ( selectedTab.url ) }
    }
}