We were actually there to see our X-ray telescope, eROSITA, being launched on the Spektr-RG space observatory. Unfortunately the launch was delayed by a month and we didn't get to see the launch that time, but we got to see the rocket on the launch pad before fuelling. We went to some museums instead and had a tour around. It was successfully launched a month later and we're currently looking at the first data. I was there for two nights.

I can't comment on the travel agencies, as ours was an official delegation. We went via Moscow from a special terminal on a Tuplov plane. We got to walk around Baikonur city, around the launch pad (not too close to the rocket), and inside the museums. We were taken around on a bus by the Roskosmos guides who would interpret things.

As for the museums, we got to walk around the Energia complex inside for an hour or two. They have lots of old terminals and control computers for the fuelling, blast doors and that kind of thing. They have a another main spaceflight museum they went to, which anything you could think of to do with Soviet/Russian spaceflight in it. They had lots of rocket motors, medals, space suits, displays on Gagarin, Laika, Sputnik, a Soyuz capsule, space food... They have a Buran shuttle outside you can go inside, though I'm not sure the interior was that complete. We had a few hours there. They also have Gagarin's house, where every cosmonaut is supposed to stay in before launch. We also went to the place where they decide to give permission for Soyuz launches. I saw the Buran building from afar as we were being driven around.

Edit: some photos- https://photos.app.goo.gl/W8tkAdjkeZsP3Sqh6 (just from my phone - my camera photos are not online)