I just returned from a 2ish day trip. Friday night, all day Saturday, and then from 6AM - 11AM on Sunday (today).
I'm planning to do a full write up, but here was the gist:
Friday night I just made the last 30 minutes before dark, so I got acquainted with the boardwalk and found two screech owls using my thermal.
Saturday was great, and I was out there from 6AM - 9PM nonstop. Weather was cool (50-65 F), there were some rain showers, and although there were what I thought was a lot of people - there weren't many "jams", and you could usually scoot by.
Sunday was not very fun at all. If Sunday had been my only experience, I'd be inclined to never go back. It seemed that 2-3x as many people showed up as on Saturday. It was also much warmer (70-75 F) with pretty much direct sunlight. You could barely move anywhere on the boardwalk without brushing shoulders with someone or getting stopped by a crowd. I walked the boardwalk once, and then spent the rest of the time on some of the lesser used trails. I saw less birds and they were further away - but it was worth it to avoid the madness on the boardwalk. In the future, I will make every effort to go on a weekday instead of a weekend.
As for equipment, here was what I saw from most common to least:
Bridge/Zoom Cameras (Nikon Coolpix P1000, Sony RX10IV, etc.)
DSLR bodies + Sigma 150-600mm lens
Canon R5 or R6 + RF 100-500mm lens
Nikon Z8 or Z9 + Z 180-600mm lens
Nikon DSLR + 500PF or Nikon mirrorless + 600PF
Misc bodies + 100-400mm zooms
"Big" Primes (400 f2.8, 600 f4, 800 f5.6/f6.3, etc.) - of hundreds or thousands of people I counted less than 20 total, with the majority being 600 f4.
I saw very few Sony users, and less than 5 Olympus users. I would expect a Sony body and 200-600mm to be a good choice. Same with Olympus and the 150-400 or 150-600.
I brought all of my wildlife lenses, since I'd never been there and wasn't sure what to expect. I've also never chased warblers, or small birds in general. I'm used to mainly shooting mammals or larger birds of prey.
Z 100-400
Z 180-600
Z 400TC
Z 800PF
I quickly determined that the 800PF would be just about useless because of the 16.4' MFD and difficulty of tracking subjects in close proximity. The vast majority of birds were 8' - 15' away. With my 400TC, I only had a single time when the 8' MFD proved inadequate. I would eventually learn that MFD is probably one of the most significant factors for shooting at Magee.
I would caution that if anyone has a 600 f4 prime they want to bring - they may reconsider. I spent a lot of time shooting with others who had 600 f4s, and they were constantly missing shots because of the MFD.
The 100-400, although light - often didn't provide enough reach.
The 180-600 is just about the perfect lens for the job if you don't have a big prime.
Since I did have a big prime, I used the 400TC 100% of the time, carrying it with a peak design sling across my body. This made it easy to walk the 18 miles that I did, and then still shoot handheld. I haven't gone through my pictures to see what percentage of keepers ended up being 400 vs 560. But I was essentially using it as a zoom lens, where I'd track the bird at 400mm and then flick to 560mm if I wanted a tighter crop. I would guess my images will be 70% at 400, 30% at 560 but I'll report back once I tally for sure.
Technically you can use monopods, but I saw very few. With how fast the birds move, it seems to me it would be a hindrance. I believe tripods are not allowed at all during the peak time.
On Saturday, I was able to do most of my birding either by myself or in small groups. This was preferable and provided lots of opportunity to get good shots. On Sunday, when it was more crowded - you basically had to pick one spot on the boardwalk and pray that whatever subject you wanted would fly by.
Overall it was still a great trip, and just about every bird I saw was a lifer for me. I will definitely be back in the future, but will do as much as possible to avoid the crowds. Getting there each morning at 6AM ensured I was usually one of the first 5 vehicles, and I could reliably be on my own until 7:30AM - 8AM ish when the crowds started. By 10AM it was a mad house.
Regarding dual wielding cameras, I saw less than 5 people do it and as Jim mentioned above, it looked like a lot of extra work and stress for no real gain. A good telezoom with 500 or 600mm on the long end would be about perfect.