Ive often heard that the plastic herons dont work - the theory is that herons are quite solitary birds & feed alone - - Im not convinced.
I have always found that the tubular clear plastic feeders with the metal cap on the top (as in pic) tend to be pretty squirrel proof, & the larger birds struggle to use them.
If you use a feeding table, then any bird will feed from it.
The only prob with the hanging feeders, is that if mixed seed is used, the feeding birds are quite fussy what seeds they eat & will flick out what they dont want, so a lot will end up on the floor - for the pigeons & other undesirables
Basically, however you feed the birds, you will always end up feeding some undesirables.