I'm in a condo on an upper floor of a high rise - my stackables are on unglazed porcelain tiles and I don't notice any vibration from my stackables nor the machies in the condo above me.

Definitely put a drain pan under the washing machine.

Another important feature about placing machines on wooden floors is the joist system. If you have a machine sitting in the middle of a joist span it is prone to flexing, sort of like a trampoline. It is best to have machines at the end of a joist setup, at a load bearing wall. Then the machine is over the most stable part of the joist. The material you use to cover the floor is secondary. A machine shouldn't move, if it does its not balanced, or the floor system is moving.

LOL, it could be cool to use one of those high-density heavy weight gym mats with a pan.

We are doing tile with a floor drain.