Nothing will happen. The upgrade will be transparent as far as PL goes.
Media Creation Tool > Build DVD or USB and run set up from any account with local admin privileges.
If this is OEM, the system will activate with a digital license automatically on first restart. If home built, you can use your W7 key to activate windows.
Before you begin: Run windows update and restart. Not necessary, but can speed things up a little bit.
Things that can get in the way:
Anti-Virus software. Any 3rd party AV can cause the upgrade to fail. The auto rollback capability is very good, but its easier to just remove it and reinstall after the upgrade completes.
Remove Windows Defender if installed. Its going to be replaced with Windows Security anyway.
If your system BIOS hasn’t been updated in over a year, might be helpful to update that first as well. Again not necessary, but can help depending on the age of your system.
Have a back up image of your W7 install. Macrium Reflect is free, so is windows back up which is included with W7.
I’ve done about 45 of these upgrades this month. Build 1903 is solid and the upgrade process is painless. SSD or m.2 takes about 55 min. Plattered disks can take up to 2 hours depending on processor, memory and internet connection. Wired connection works best.
Time to move on. Just get it done.