Considering 1994's common machines, definitely an ISA-limited 486SX of some kind.

Note that hitting R should bring it to 640x480 which will be noticeably slower for that spec, which would be more comfortable for the P60/486DX4-100 crowd of the time......

No, EA didn't resolve the speed issues in the 1996 classics rerelease either.

The 640x480 mode is puzzling, if you slow performance enough to have game time not run away the responsiveness is awful. Did this happen on an actual 486 too?

Back of my copy says the following:
Required: 386/33 MHz or faster (486/25 MHz or faster recommended)

So they were probably targeting the 486/25 MHz models, or somewhere in between that and the minimum.

EDIT: That's from the 1999 release, so grain of salt advised. Original box of the CD version just advises a 386DX or higher.

EDIT 2: Found an original floppy copy on ebay. Photo of the sysreqs say: 386 25MHz required, 386 33MHz recommended. So I have to revise my above statement. Definitely targeting below the 486/25

I learned from Caesar 2. A game with similar specs from the time. It actually runs fine in faster computers, till you notice some some animations, like the flags over the praefectures...

Between 3000-5000 cycles seem to work the closest to how it was, but some animations will still run slower than in real hardware... All I can say is that you should experiment with fixed cycles, and less than 8000

Its bit slow on my 55SX with 386SX 16, so maybe a 486DX33 would be a perfect fit.

I confirm it works pretty well on my 486DX-33 in regular resolution mode. In highres ('R' ingame) it's unplayable though, as pretty much expected.

Did it have Highres ? only CD-ROM version or ?

No, in all releases I believe. I'm using the initial 1994 multilanguage floppy release.

Ah never noticed