The difference between the a or b is the dimming. The a version has built in dimmer that will allow you linear dimming from 100% output down to 50% output. The b version just comes with dimming leads. So you would have to install your own dimmer. This would cost you extra, but also allow you to dim down to 10%. The major benefit to the b is that with the dimming leads open they actually put out an extra 5-7% current. So you get some bonus power.
I usually recommend the a version, especially in your first build. It’s easier, cheaper, and you shouldn’t ever have a reason to dim below 50%. The extra current in this case is like 50ma, so it’s not really going to change anything.
Other stuff looks good. We talked about getting 18awg solid wire rated for at least 300 volts right? And then you’ll probably want something different for the ac input side of the driver.
