Furnace dripping water with AC on Rheem Criterion II

Really not familiar with these systems, and hopefully this is a basic question for someone to enlighten me. Just turned on AC for first time this year, and I noticed that the furnace is dripping water - kind of blowing out droplets out of the back of the furnace out of a small tube. Linking photos. Is this just condensation? Is it a symptom of a larger problem? Should there be a cap on that pipe so that it just doesn't leak?

The system is the Rheem Criterion II Plus 2. AC doesn't really even cool the house either - even though the condenser unit outside was replaced last year...