Another question to answer:
And finally, how much far advanced Imperial science/technology compared with other Presidium Powers?
Well, now, that’s a complicated question, covering a whole lot of different fields and people and… yeah. I probably can’t give you a full answer, but let’s see what I can say (with the additional caveat that this is the publically-known *there* view).
The Empire, by and large, does lead the edge of advancement for several reasons, including but not limited to (a) being ideologically and personally inclined to push the edge of progress For Science!; (b) being entirely comfortable with buying, imitating, etc., good ideas other people have for their own use, unlike more xenophobic cultures which often seem to reject ideas just because someone else thought of them first; and (c) being very flexible in using new technologies (the economy is laissez-faire, the ethical standards don’t wibble about much beyond informed consent, and so forth)…
…but it’s not nearly as far ahead as it might be, because the Empire’s set-up is diametrically opposed to keeping such things secret. Even if its governance could get away with imposing the sort of controls needed to keep technological secrets out of other people’s hands, which it couldn’t, it knows perfectly well that security by obscurity never works in the long term, that keeping technological secrets reduces the total amount of innovation you have to draw on, and, for that matter, that keeping other people mired in primitivism for your own advantage is, well, remarkably morally ugly.
(In relative terms, that is. An Imperial would point out that by giving up the opportunity to be further ahead in relative terms, they’ve actually made more progress in absolute terms.)
Specifically of the Presidium powers, the Photonic Network trails a short distance behind the Empire, and may actually be ahead in certain areas: the difference often isn’t much, because they have similarly sensible policies and are very good at information-sharing. The others make up a clump a little further back, with the League of Meridian bringing up the rear of that clump because their voters often issue knee-jerk moral-panic bans due to what amounts to squickedness; often they get over it when they see that other people have been able to use such technologies without causing whatever it was that squicked them, but the tendency is enough to notably slow the rate of adoption.
(Such is as expected, really: the Ephemeral Worlds, Rejectionists, and people whose planetary economies can’t support high technologies have other reasons to explain why they can’t make it into the Great Power club.)