There are a few very good comparison tools on the "Interweb" that if you pump in the wheel and tyre sizes will should how close they compare and what difference it makes to the Speedo reading. For example, if I compare my 215/50R17 on the Gen 1 ZS EV with the 205/60R60 on your MG5 the difference in diameter is less than 3% and at the speed which would show 60 mph on my ZS speedo would with your 205/60 on the smaller 16" rims would be doing ½ mph greater ie. 60.5 mph.
The tool to make this comparison is the
"Tire size comparison" at
"tire-calc.com"
The difference in sizes and parameters between the 215/50 R17 tire and 205/60 R16 tire. Detailed calculations and graphics.
tire-calc.com
If you want to get more into these things then a more advanced tool that will let you check your clearances with alternative wheel sizes, rim widths and off-sets (the ET value) etc is the "
Rim & Tire Size Calculator" at
Wheel-Size.com
Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results
www.wheel-size.com