Assuming the capacitor is still good, these will work. If you use them with the umbrella, you'll probably need to use them in manual, and the flash meter will help tremendously. Without the umbrella, you can probably use auto with good and consistent results. Something else you can do is tape some white tissue paper to the front of these which will soften and diffuse the light.
Play with natural light first for your shoots. That will give you the least to worry about and less that can go wrong. But play with the flashes and learn how they work so you can add those to your skill set as well. As soon as you figure out how to work the actual flash, try using off camera with a cable.
You might want to start a new thread with those pictures and see if anyone knows how to work these. Its been about ten years since I've looked at one like this, so there are a few things that are confusing me.
This was taken with a Minolta flash similar to the Achiever you have set on auto. The Minolta flash and camera were one day yonger than I was--so about 17 when I took this.
