Don't distinguish between "options" and "preferences" (Windows/Mac,Linux) since TB 91 calls them all preferences now.

addon/content/dialogs/options.js

@@ -37,9 +37,7 @@ var pEpOptions = {
   },
 
   initializeStrings() {
-    let label = pEpController.platform == "win"
-      ? "optionsLabelWin"
-      : "optionsLabel";
+    let label = pEpController.platform == "win" && pEpController.MOZ_APP_VERSION < 91 ? "optionsLabelWin" : "optionsLabel";
     document.getElementById("appPreferences").setAttribute("title", this.getLocaleMessage(label));
 
     document.querySelectorAll("[label-localekey]").forEach((element) => {

addon/content/pepmsghdrview.js

@@ -200,7 +200,7 @@ var pEpHdrView = {
     if (win.location.href.startsWith("chrome://messenger/content/messenger.")) {
       // Add options menu after account settings (and before the normal options
       // on Windows).
-      let label = pEpController.platform == "win" ? "optionsLabelWin" : "optionsLabel";
+      let label = pEpController.platform == "win" && pEpController.MOZ_APP_VERSION < 91 ? "optionsLabelWin" : "optionsLabel";
       label = this.getLocaleMessage(label);
       /* eslint-disable max-len */
       let xul = win.MozXULElement.parseXULToFragment(`