Hi all,
I installed HA in my raspberry 3b+.
This is htop screen of the device:
I don’t know if my HA user experience is fast or not, honestly I think it is ok…
But if needed I could do an upgrade…
1-MariaDB
2-Upgrading to a rapberry pi4 with ssd
3-Old notebook???
I highly recommend MariaDB or any other DB instead of the built-in DB, as rhe built-in DB often had issues in the past.
If you don’t see anything in your system that is not fast enough, you don’t need to upgrade.
If you do upgrade, an old laptop has the advantage of having a built-in UPS 
With MariaDB what will be faster? Lovelace? With MariaDB where do I storage the files?
The files are still stored in the same place, the DB is only for keeping history of your entities.
There will be no performance differences, except that probably the history tab will load faster.