Having finally gotten a chance to play around a bit with OS4.1 Classic on WinUAE, on my system it's pretty poky, but then I've got a pretty old and creaky system (Phenom X4/940 @ 3ghz, 8gb DDR2 RAM).
Doing a new build in a couple of weeks (FX-6300, 16gb DDR3 @3200), we'll see how it behaves then.
Its pretty dam responsive on my 27inch 5k iMac
which has got i7-6700K Processor 4.20 GHz and 16GB of 1866 MHz PC3-14900 DDR3L SO-DIMM SDRAM