So specifically here would I notice a difference in any way between this one and Gladden?
No difference whatsoever, I would expect. Both are among the very smallest servers, Gladden just ceased to be the recommended server and Arkenstone just became the recommended server so both will have a large surge of low level characters (most of whom will abandon LOTRO within a month or two) at the moment.
If all you want to do is soloing, either Arkenstone or Gladden will work well. If you eventually plan on doing some group content I'd suggest playing on one of the larger servers instead - Brandywine is largest by some margin, and the rest are pretty comparable in size (see http://lux-hdro.de/hdro-live-us.php for stats).
I play on both Gladden and Arkenstone. There aren't too many differences, so whenone comes up, I'm kinda surprised. I ran into several really nice and helpful people when I first started on both servers. The biggest difference is in the Auction House. There have been really significant differences in prices of some items. I only hope you have the good luck in meeting nice people that I have had. Good luck
Since you brought it up, I don't know - is it possible to play any group content within 1 to 1 1/2 hour time blocks?
In principle yes, 3-mans will easily fit in that time frame, as will the most common 6-mans (Grand Stairs, Foundry). Raids, I think generally not, though lair bosses (Turtle, Draigoch) and skirmish raids are the exceptions. Those are the raids most people would actually want to do anyway, IMHO.
In practice, for a fellow Californian, probably not though. You also have to take into account the time taken to find a group. Unless it's a scheduled kin run such that everyone's ready to go within minutes of when you log in, that's just not going to happen in most cases (and assumes you can arrange your own playing time to fit the run's schedule). Right now, if you were to look for level 75 group content in 1-1.5 hr. blocks in Pacific prime time I'd expect your time to be wasted, with the possible exception of a guardian, minstrel, or heal-traited runekeeper looking for an Isengard 3-man run. If you happen to play in the late afternoon/early evening and thereby take advantage of East coast prime time hours you might well do better, though.