ardashir wrote:First, do they ever get or develop any new magic or psychic powers as they gain levels? Or are they always limited to what they have at first level?
They are limited to what they get at first level, that in of itself is not unusual. They might also be able to gain additional powers in either category by non-class-level means:
-equipment (TW Devices, Psionic Devices, magical artifacts, and magic potions)
-environmental exposure (this one is pretty rare, but there are places on Rifts Earth that have caused mutations including installation of said powers)
-Gene Splicers (not recommended, but certainly possible at least for psionics though I'm not sure on Magic off hand)
-Bio-Wizard Implants (thinking of Zembahk, Eye of Eylor, and maybe one a few others found in WB2/21 or WB12), TW Bionics (BSB or WB20), or Psi-Implants (found in WB12)
ardashir wrote:Secondly, can they take on any human form when they transform or just the same one every time?
Per their more recent WB30 (D-Bees of North America) Entry they can (emphasis mine) "assume a completely human appearance, and
take on different facial appearances and skin tones". So yes they can vary their human appearance to some degree at will, weather they could pull off a specific person is not stated which would lead me to think the answer is No (at least not without appropriate skills).