The 2021 iPad mini uses a A15. Its the economy iPad 9 that is using a A13. The 2018 12.9" iPad Pro used a Liquid Retina display.Too bad the new Mini has A13. My 2018 iPad 12.9 has a A12X...I don't suspect there will be a huge (if any) performance increase? I just wanted something smaller, but I guess I'll keep my 12.9 for a little while longer.
Is there any advantage to the new Mini iPad over my 2018 12.9 iPad Pro? I don't use the camera on it, at all. Is the screen on the Mini better than mine in any way?
The advantage the 2021 iPad mini has is processing power over the 2018 since it uses a A15 compared to a A12Z. Thats 4GB Ram vs 3GB RAM built in also. The mini actually can be used for photography easier as it's not so big. Compare your 2018 iPad Pro vs the iPadMini 6 vs iPad 9 in the below URL.

iPad - Compare Models
Compare resolution, size, weight, performance, battery life, and storage of iPad Pro, iPad Air, iPad, and iPad mini models.
www.apple.com