I thought I was the only one using BD Sizer. It's been around for years and is the only software that avoids a lot of buggering about with trying to second guess file sizes. I haven't quite worked out batch processing yet and, to be honest, I only resize for the web.
I find 630 - 650 pixels along the longest edge is about optimum (especially in landscape orientation) as. otherwise, bits hang over the edge.
Actually, I think you're the one who introduced me to this program in the first place.
I must admit batch processing is a bit awkward.
You just drag a bunch of photos from explorer into the "apply in batch" box. Select the output folder. Select the settings you want applied and press the apply in batch button. That's for version 231.
For version 333, it's a bit different. The photo list is on the top left. You just drag files there like usual, select the options and click "run now".
From testing both on my machine, I find the earlier version faster than the new one...