Yeah, spawning is quite slow with a single spawner but it the best we have so far If you have a sweeping edge sword, wait until there are a good number of them and you can kill them in all one swing but still not the fastest. The problem with spawners is that you have to be within a certain number of blocks for them to be active (I think 16 but don't quote me on that) so you can't have another spawner unless you luck in to finding 2 close together. There are faster XP farms out there - Guardian farms, Pigmen gold farms, Ender Enders - which would be useful once we have mending tools as you can repair fully worn tools in a couple of minutes. The problem is they are either huge farms or a pain to build but certainly something we can work towards.
As for the drops, I'll double check but I think the right most column of chests has no filter so anything that isn't bones or arrows will end up in there. You will get mobs with armour on though - sometimes leather, sometimes iron and sometimes gold. However they dont' always drop the armour they're wearing when they're killed sadly Though on a side, if you get any gold armour you can smelt it in to gold nuggest and craft them in to gold ingots