Latest OS but all runs the best for old Macs

I have a few old machines and I was wondering which version of the OS is the latest but also runs the best on these machines?

Mac Mini Late 2009 currently running Big Sur 11.7.11

2.26 GHz Intel Core 2 Duo

8 GB DDR3

Solid State SATA Drive

MacBook Air Late 2011 currently running Big Sur 11.7.11

1.6 GHz Dual-Core Intel Core 5

4 GB DDR3

Solid State SATA Drive

MacBook Pro Early 2008 currently running Big Sur 11.7.11

2.5 GHz Intel Core 2 Duo

4 GB DDR2

Solid State SATA Drive