Thanks for using Aspose APIs.
From what you have said, we are not sure whether you are using the calculating engine of Aspose.Cells or just getting data from template file by Aspose.Cells and then do calculation by yourself. If you do calculation by Aspose.Cells, then all data (including formulas, names) should be loaded and we are afraid there is no better way to improve the performance much more. If you do calculation by yourself and only need to get data from template file, then you can choose to load cell value only, which may improve performance of loading template file. And if you can manage the grid data by yourself too, then you can use LightCells APIs for loading template file, which may give better performance for both speed and memory cost.
Anyway, please check the following article relating to LoadDataFilterOptions that will enable you filter data while loading workbook.
So, you may have options according to your specific situation:
If you want to calculate formulas by Aspose.Cells, at least you need to load CellData and DefinedNames:
If you only need to get cells data from the workbook, then you can load CellValue only:
If you only need to read out all data in the template file only once and then manage those values by yourself for being used later in your application, then you can use LightCells to fetch cell data from the template file. Meanwhile, you will still able to use LoadDataFilterOptions to filter data.