Hi Eagles2020!
It's good to see you in the QuickBooks Community space!
Yes, when you change the structure of your accounts, that will reflect in your previous fiscal year's reports as well. You can try this on the sample company files before changing anything on your record to gain confidence and to avoid making mistakes.
If you need more assistance, feel free to go back to this thread. You can also check about customizing reports for additional reference. Have a good one!