Are prototyping boards suitable for 200V?
No, don't put 200 V between adjacent pads.

When nothing is going wrong, it should work.  It varies with pressure, temperature, and humidity, but air can roughly hold off 1 kV per mm.  Using that as a guide, 200 V would be 200 &micro;m or 8 mils.  Most likely you have 10-20 mils between pads.

However, since failure can be dangerous and cause all kinds of undesirable things, you want to be conservative.  First, the 8 mil rough guide is the expect-to-fail point.  Obviously you don't want to be there.  It doesn't take much dirt or accidental solder ball or something to turn a 20 mil gap into a 8 mil gap or less.

Usually you want &frac14; inch or 5 mm between line voltage and anything a human can touch.  That's deliberately very conservative, but again, that's because the cost of failure is so high.

Don't use a breadboard like that for anything you're not willing to touch directly, which pretty much means stay below 48 V.