It’s always had a lot of lag for me ever since I started using UE about 3 months ago. If you don’t want lag you have to use the Quixel Bridge app and start it from your desktop and transfer each asset to UE. Also for some reason the local assets from the desktop app in your local section are separated from the quixel that you use inside UE. Don’t know why this is the case but you’ll have 2 different local assets lists.