Does 5e large scale battle exist in spreadsheet form, or is it more ethereal like making strategic and creative decisions and inspiring the DM in roleplay?
There are no 'Official' rules published on managing mass combat for D&D 5E. However, Wizards of the Coast has published Unearthed Arcana (unofficial/playtest) material for handling mass combat
Bear in mind that this is playtest material and may not be well balanced. The ruleset is simulation-based where units of soldiers/creatures/etc. are abstracted as 'Units' of varying size and strength. You then run battle between these units.
I have not personally used these rules, and cannot speak to how well they work.