My mere advice:
Concoct your table and cell styles while NOT in a Type tool that is also NOT in any sample example text. IOW, be in a black Selection tool and have nothing selected. Dream up your style attributes in your head and build them in the Table and Cell Styles dialog box. Clean. No conflicts.
Place command your Excel file and hold down the Shift key when you choose the file to place. This brings you to Word/Excel options where you should probably opt to bring in the table unformatted, in order to leave behind any attributes that tend to override and confound your styles.
Once the table is on the page, select the table with your Type tool and click once on the Table Style that you made. This, in turn, will apply your Cell Styles. Don't directly apply your cell styles first. Only apply cell styles afterward if you are making a complicated table and have bits that the Table Style cannot make for you. Finally, as you have already been doing, click on the Remove Overrides if and when you see the Cell Style panel showing None+. That should strip any remaining oddities, if any.
Excel tables must have the top row selected and you make the top row into a header row, if the table is long and flows onto a new page or column. Unfortunately, you cannot do this in advance.
Yes, a bit Rube Goldberg. (Wasn't he amazing?) But that is because a Table Style can be overridden with up to 4 other situations on top of it: Directly applied cell styles, directly applied attributes, original attributes that came in when you placed the table, etc. Your goal here is to be clinically pure in only applying your nest of attributes from the top down; only from the Table Style down.
Be sure to read the helpfile about Table Styles. It is very enlightening.
Hope this helps,