With regard to Warlock spell slots, it really depends on how many encounters there are between long rests. At lower character levels, they can quickly eclipse the number of spell slots of even primary casters, given 3+ encounters per rest. Also keep in mind that a Warlock's spell slots are of the highest spell level they can cast. So, primary casters may have more slots at some levels, but they certainly don't have as many high level slots, unless there is only 1 encounter per long rest.
