Well, currently, Aspose.Cells for .NET does not parse html tags to import data to Worksheets although you may convert an excel file (xls/xlsx) to save as .html file formats using e.g…, workbook.Save(“d:\test\myfile.html”,FileFormatType.Html); We willl look into the feature soon.
And, yes, you do need to use Cell.PutValue() method to manually export data to excel spreadsheet.
Well, I think you may try to merge / unmerge the cells using Cells.Merge() and Cells.Unmerge() methods. If you are creating some ranges, you may utilize Range.Merge() method to merge a range as well. Moreover, you may use Cells.SetColumnWidth and Cells.SetRowHeight methods to extend cells heights and widths to format a table for your need.
For your reference, please check the following doc topics: