Fastest OS for MBP 11.1 (A 1502, Mid 2014, i5 2.6 GHz) ??

[Dr. Koch]

I'm running Mojave 10.14.6 on my "obsolete" MBP 11.1, which is sometimes really slow (PhotoShop 6, iMovie).

Considering downgrading to Sierra 10.12 or even down to Yosemite 10.10. ...

I somehow have the impression this APFS file system is strange: there's 2 partitions on the Apple SSD (120 GB): a "Container disk1" (which contains "VM", recovery, my MAC HD and 1 "not activated"), and it says "121.12GB shared by 4 Volumes" (same as the MAC HD, which also has 1 "other volume" of 3.8GB besides the used space) ...

Anyone done that? Experiences?

Other ideas what might slow down the machine? Suggestions?

Thanks 'n' best from Berlin, Germany!

 

[Audit13]

The version of macOS may not have much impact on the speed of the machine when using CPU-intensive, GPU-intensive, and/or ram-intensive programs.

How much empty space is on the SSD? How much ram is available when the MacBook is running slow?