I do believe unless otherwise stated an artifact with spells casts them at the lowest lvl possible for the spell. But as a gm you may have it however you like for home games.
A bit late, but you could pretty easily replicate one or two of the given powers for additional scales; the only rule is that one person cannot carry multiple scales to gain multiple powers. So if two of your PCs would benefit from Cloudwalking, it won't be overpowering to let them both have a scale that does that, for example.
But in general, what the scales do mechanically is offer the player three uses a day of a 2nd-level spell from the wizard/sorc or cleric/oracle list that might be reasonably appropriate and interesting for their character (so cloudwalk/levitate's good for front-liners avoiding foot-level hazardous terrain, resistance/resist elements is generally useful, sacred weapon/align weapon is good for a melee fighter, etc). So give those two spell lists a look and see if anything else seems like it'd be interesting or needful for your PCs. Just remember to make sure they can't be used for evil (easily, at least).
Do note that, if you're coming in from the CRPG, the scales DON'T have the revival effect they did in that in the rules as written; you could rule that the scales can be "discharged" to have a Raise Dead effect but using them in this way makes them inert, but that's potentially a lot of free raises from the off in an AP that already has some power curve issues.