Hi.
When you bought your device have you transferred data via Smart Switch? This might have facilitated some bug transfer, although I use Smart Switch every time and my devices work fine, although I am aware I might transfer residual data as well.
How is your memory like on these devices?
Have you tried using the RAM plus feature on Device Care App and also cleaning memory and RAM on this app weekly at least?
I have noticed that is not good to overload a tablet with Apps, and not even a phone, but the phone comes better, so it might help to uninstall apps you don’t need on the Tablet, while for the phone is strange what is happening, and I believe it's got something to do with the memory of them phone. Strange how both your devices have the same problem.
Try performing Wipe Cache Partition on your devices as well.
You can also download Good Guardians App and do some system optimization from there as well. It's a Samsung native app, not 3rd party.
Here is a link for reference.
https://eu.community.samsung.com/t5/galaxy-a-series/for-those-having-issues-with-oneui-7-being-slow/...
