Last night Twitch and/or my ISP wouldn't allow me to watch the stream, so thanks for the YT mirror. Very entertaining. I also liked that you showed the old WIP levels and the history behind them. Looking forward to the second part - not looking forward to the HD textures, though. At the very least, I hope you're not going to use one of those god-awful "HD" packs like Epsilon or the like!
The slight framerate issue seemed to start once you switched the resolution to 1280*800. Not sure if it went on for the rest of the stream; I certainly didn't notice it anymore in the BB levels.
About Quest. Not sure which version I started with, but it definitely was one of the old ones by Carollo/Harrison and it did have a textured view, though (being a DOS program) it was slow and you had to toggle it each time. Pretty sure it also had a texture alignment feature, albeit a very basic one initially. I remember specifically how it was impossible to rotate textures, so one had to do it manually like you did. In some old map, I made an elevator shaft with angled beams on the walls and aligning the textures took a whole day instead of just a few seconds like it should have.
When Alexander Malmberg took over, many great features were added or refined (some of which took me over 10 years to discover). For example, there even was a textured "polygon" mode that allowed texture work with a dynamically-updated camera view. Super slow, of course. It also had a lighting preview, a "click brush" feature to draw new multi-sided brushes on a 2D plane, support for a fairly high number of games up to Q3 engine, and more. Not to mention, the tallest-ever Quake map
was made in Quest. B) So, yeah, it deserves more credit than it's usually given.