a) is working as intended (I always wanted to say that
). If alwaysonbottom=true is not set, you risk covering other windows. ProfitUI is not meant to be used with the letterbox enabled. The bottom bar can be unlocked and extended upwards to create it's own letterbox area (transparent or black). However, it's true that we don't have a similar top letterbox effect. EDIT: Btw, the letterbox is working fine for me and is behind the bottom bar...
b) Hmm, I'll check the code for conjurors. It's working on my toons. Both buttons are supposed to set your adv/ts class and a level range up to 10 levels below your level.
c) is working as intended - or rather as far as I bothered to implement it so far. As written in the changelog, it's only a visual thing. The correct volume settings are remembered, just not shown. Same applies to the other sliders of the startbutton.
2nd pet attack button is useful after recalling your pet, as it resets the protect me/self settings.
We don't have a documentation for the UI, but I try to document all relevant changes in the changelog on the main info thread. Just reading through there should give you an idea about several functions of the UI (at least those that were recently added, there's loads more originally put in by Profit).