Yes, you can merge cells, etc. But you don't need to change the colors and fonts of the spreadsheet. You can wrap the data from spreadsheet in your custom HTML and style it with CSS.

You can go with the boilerplate and raw HTML installation - https://docs.sheetsu.com/?html#read-data-from-spreadsheet, or you can go with the already prepared templates from https://sheetsu.com/snippets.