Angus speirs

This is my first blog to this forum. I model in DC and am building a terminus to fiddle yard GWR layout set in Dorset. I have an old Hammant and Morgan clipper controller and a Guagemaster combi walkaround unit, which I used on my previous shunting layout. I have a variety of locos from over 20 years to 1 year old. Would I be safe to use the 12v dc connectors on the Hammant and Morgan without damaging the modern locos or should I use the Gaugemaster combi only? If I am advised to use the H&M, there are resistance and wave switches on the controller, which are the best settings for them to ensure no damage is done to the loco motors?