Hello @mehtasal, welcome to the QuickSight Community!
If you are returning multiple tags in a single row value, there won’t be a clean way of filtering those value. If you wanted the filtering capabilities to work better with your data, I would recommend either having a row for each tag that is linked to a name, or you could create a column for each tag and then return true or false for each name to keep them on the same row. That would either need to be done in your SQL query for your dataset or in the data source itself.
The other option I can think of would continue to return a row value that contains “Tag1, Tag2” if Tag1 was selected in your filter. Set your control to be a dropdown and write out all of the possible Tags contained in the field. Then create a calculated field that would use a contains function to check if Tags contains the value returned from the parameter, then return tags else null.
As for your 2nd question, there currently isn’t any more functionality than what you previously stated in regards to sorting for a table. Since this is an added capability you would like to have access to in the table functionality, I have tagged this as a feature request. Thank you!