BeagleBone Blacks. These only have 1GB of RAM and they’re definitely fast.
512MB. Unless you got some crazy manufacturing defect.
I have the highest specs
Meaning what, exactly?
As far as the SSD, do you recommend anything other than the SSD kit from the Apple Store? $750 for 512GB kinds hurts
A common approach is to put the OS and frequently-used applications on the SSD, and keep your HDD for regular stuff. Faster start-up times with a smaller (cheaper!) SSD. With this approach, there’s hardly any reason for something bigger than 128GB (if that).
There are also hybrid designs which use the HDD for storage, and have a small(ish) SSD used for caching. This setup works well because a) it’s the size of a single drive, and b) the caching works automatically.
will any SSD run alright?
As a general rule, “as long as it fits in your machine.” Check the physical size and connection types.
As a disclaimer, though, I don’t deal with Macs; one reason being how much effort they spend on controlling what and how you can upgrade. When they started gluing parts in, I gave up hope. And I’m sure @Joe_Temp is right that you’d lose your warranty if you do it yourself.