Starting Father's Day weekend, I've had a decent amount of water going into the overflow pan and out of the drain along the roof. Added some vinegar to the vent pipe in the attic then checked the sink that the primary drain goes to and it was slow, but not clogged. Added drain cleaner a couple of times and water then drained normally. AC drip stopped. Now, it has started up again off and on. The pan drain is clear and it's not really even filling up any, but there is a steady drip or small stream of water going to the pan.

Is this normal when it's really humid like it's been lately, or is there something else I can check or do?

Primary line is probably clogged. It best to take it apart and clean it with compressed air.
I always put about an ounce of bleach down the T after the coil to help keep it clean.

Does the primary tie into a bathroom sink ?

Check that point as well as the trap and drain on that sink for blockage.

1 cup of vinegar quarterly will solve your issue in terms of preventive once you've fixed the clog

I pour bleach & water down mine every month. In my old system, it wouldn't turn off the unit if it was clogged and I would get wet floors. That taught me to do the maintenance monthly. New system can detect if the drain is clogged and shut off. So, no more wet floors, but I like my AC running, so I'll keep up with the maintenance.

Spring and Fall I dump a half gallon of straight bleach down each ac. Then I follow it with a half gallon of water about 5-10 minutes later. Seems to be enough for my 2 systems.

One unit that always clogged I just eventually replaced the pvc. Got tired of the clogging. Cheap solution.

I see this often

The 3/4 pipe will often be 1/2 to 3/4 full of sludge/slime for sometimes half/3/4 or even the total distance especially if there is not enough fall or sagging/low areas where the pipe is not properly supported. I redid one back in February that was nearly 3/4 full inside over the entire 20 ft run. Owner was constantly having to have it cleaned out.

Mine is also over 30' long with 3-4 90 deg turns in it too and not sloped well. Got new handler a couple of yrs ago and set it about 2" higher and re ran the pvc so far so good

I also put in a ball valve (to block air going backwards into handler) and a whatever connector to connect one of these to blow things out. https://a.co/d/gilMrOk

In addition to the bleach schedule, this is where a leak detector is cheap insurance. I buy $30 sensors that tie into my alarm system and put one in my AC pans, water heater pans, and bathrooms. Brings a lot of peace of mind.

I took some electrical fish tape and rain it up my primary drain until I could access it in the attic, cut up a small rag soaked in bleach and pulled it back through the pipe. I was amazed at what came out.

I have to blow out my A/C drain line once a month and pour some bleach through it. I'm sure the drain line needs more slope. I am getting ready to add a UV light to kill bacteria etc. to keep the coils clean and improve air quality. Has anyone installed one of these?