grid stoppers are used to prevent oscillation in the tube, and should be placed as close as possible to the tube pins, this is widely accepted practice (done in your dacs)
re the cathode resistors, as it's directly in the signal path I would follow the less is more principle and minimise the number of solder connections from cathode to gnd.
on quick glance it also looks like he is doing the pentode/triode connection (g3 -> k) on the tag strip instead of directly on the tube socket, potentially adding a nice long wire (antenna) for RF pickup.
as to how it affects the sound, who knows it probably sounds very good..
the contruction method he used is nice and neat, no doubt inspired by the tektronix of yesteryear, but if you have a quick search for images you will find they connected any critical resistors directly to the tube pins, and kept lead length to the very minimum.
quick google search:
