Planescape: Torment wasn't basically Baldur's Gate: if you played it, the game felt like a totally different team was involved. The writing, characters, items, etc, had a flavor all their own. It used the Infinity Engine just as the IWD series did, which doesn't make the IWD games anything like the BG series. PS:T was actually far more sophisticated than BG1, and the Bioware team praised it to the skies. Credit for the interactions in BG2 went to PS:T, which was developed by Black Isle Studios.
You can play Ultima VII by simply purchasing it, then downloading and installing
this. It's necessary because Origin Systems was using a proprietary memory manager at the time, which is not compatible with any version of Windows. You'll find a lot of features from the Bioware games in Ultima VI and VII (the latter is far more attractive).