Use the Google Sheets API, which allows you to specify the primary dimension of the response. To do so, first you must enable the API and the advanced service
To acquire values most efficiently, use the spreadsheets.values endpoints, either get or batchGet as appropriate. You are able to supply optional arguments to both calls, and one of which controls the orientation of the response:
const wb = SpreadsheetApp.getActive();
const valService = Sheets.Spreadsheets.Values;
const asColumn2D = { majorDimension: SpreadsheetApp.Dimension.COLUMNS };
const asRow2D = { majorDimension: SpreadsheetApp.Dimension.ROWS }; // this is the default
var sheet = wb.getSheetByName("some name");
var rgPrefix = "'" + sheet.getName() + "'!";
// spreadsheetId, range string, {optional arguments}
var single = valService.get(wb.getId(), rgPrefix + "A1:C30");
var singleAsCols = valService.get(wb.getId(), rgPrefix + "A1:C30", asColumn2D);
// spreadsheetId, {other arguments}
var batchAsCols = valService.batchGet(wb.getId(), {
ranges: [
rgPrefix + "A1:C30",
rgPrefix + "J8",
...
],
majorDimension: SpreadsheetApp.Dimension.COLUMNS
});
console.log({rowResp: single, colResp: singleAsCols, batchResponse: batchAsCols});
The reply will either be a ValueRange (using get) or an object wrapping several ValueRanges (if using batchGet). You can access the data (if any was present) at the ValueRange's values property. Note that trailing blanks are omitted.
You can find more information in the Sheets API documentation, and other relevant Stack Overflow questions such as this one.