I verified in Pega 7.4.

In RTE, options are set using an array in pzpega_ui_richtexteditor.js. Below is the code snippet. To confirm you can do a private of the js and remove some values from the array and verify.

As these options are standard and provided by CKeditor, Pega Platform does not provide any setting to limit the options of Rich Text Editor control. 

Code Snippet:

pega.ui.RichTextEditor.prototype.ckEditorToolbarConfig = [
    ['Bold', 'Italic', 'Underline'],
    ['Font', 'FontSize'],
    ['TextColor', 'BGColor'],
    ['BulletedList', 'NumberedList'],
    ['CopyFormatting', 'RemoveFormat']
];

Hi Ganesh,

If RTE should limit those options at all the places? you can use the following style. place the below code in the userworkform. Each id constitutes to a option(to know more, inspect and check in DOM).
<style>
.cke_combo_button ,#cke_17,#cke_20 ,#cke_21 ,#cke_26,#cke_27{
display: none !important;
}

</style>

-Rakshith.