I have used the Bin Primer (with shellac, red label) on varnished cabinets, followed by paint and then a waterbased polyurethane and I've had great results. I just saw that Bin has another primer that's 123 Plus used for interior and exterior. I'm wondering if this one will be any better than what I have been using since it's for exterior too. My only concern is that it is not shellac based as the other Bin primer. I'm going to use it the same way as before; primer over varnished cabinets, followed by paint and polyurethane.
Bin is a Zinnser product, as you said, it is shellac based and usually used for very bad stain coverage, not necessairly used as a primer for normal painting projects, not needed.
123 is a Zinsser product, a good stain blocker and all around primer, better for what you are doing and the smell will not kill you outright.