Hey, I was wondering if theres a way to adjust stuff like magic mob spawn rates or sp gain boosts?

Yes, basically everything in this plugin is customizable.

If you have added the spawnmobs example (/mconfig example add spawnmobs) you can edit the spawn rules with /mconfig editor world overworld_mobs (also nether_mobs and end_mobs)

/mconfig editor wand talisman to edit the mana talisman

thanks!