In general, I also enjoy their work, and I’m excited for this kickstarter (in spite of how I view the top leadership at Kickstarter).I don't think Kobold Press has the same level of resources for playtesting that WotC has, so I wouldn't expect the same level of final polish. But I've loved their books so far.
That doesn't mean they are unbalanced.There are several spells that are just strictly less or more powerful/useful versions of PHB spells, but with sprockets or whatever.
Sure.That doesn't mean they are unbalanced.
A 3rd-level damage spell that was a superior version of fireball would be unbalanced.
A 3rd-level damage spell that was a superior version of vampiric touch might be almost usable.