Honestly, this sounds a lot like normal chick antics. They're testing everything at this age but also little scaredy cats. I'd keep them off the top by using the cones and just leave it there. I feel pretty confident that they'll figure it out, but if you have older hens that are also afraid of it, that can certainly be infectious! The little ones will carefully watch the older ones and pick up a lot of cues from them.
They also may be a bit young for the stick-your-head in feeder. I wonder if it scares them because when they do that, they can't keep a lookout for predators at the same time. You know they don't need to worry about that, but they don't. That one also just may take some time. I've not used one of those, but I would think it would work better when they're older and can move in and out to grab food faster. And after they've gained confidence. Maybe try moving it to a place that might feel more secure for them?
And I get you with that plastic standard feeder. I hate those with a passion! I won't even use them in my brooder. All it does is make a mess, but this idea might be worth a shot:
https://www.backyardchickens.com/threads/chick-feeder-no-waste.865378/
I hear what
@Al Gerhart is saying and he's very knowledgeable, but I've been using GF treadle feeders for about 6-7 years and never had anything but fine experiences with the partially-open training technique. Also fine customer service with my GF feeders, although I ordered directly from them and not the big A. I had one arrive damaged one time, sent photos to them, and they immediately shipped another one. They didn't want the damaged one back so I donated it.
Idk if this helps, but this is the one I use until they're fully incorporated with the full grown hens:
https://www.strombergschickens.com/poultry-supplies/turbo-8-lb-chick-feeder-single/ You'll want the lid also or fashion one. The lid that goes with it doesn't fit very securely so I also place a cone or scat mat on top of it. The feeder is pricey for what it is but lasts forever. I just raise it up onto blocks as the chicks grow.