Our weapon of choice in this is a good quality wooden framed wire excluder. They are the best.
Despite them causing problems in BS setups, perforated zincs are almost as good. However, the ones designed to be a neat fit inside the perimeter of the box are not to OUR liking. They require an unerring accuracy of placement, and a care not to slide boxes about that just eats time once you add it up at the end of the day. We had some of those and discarded them once we found we could take our old and long since obsolete zinc ones for Smiths, clean off one end thoroughly, and extend them using gorilla tape (the savage cloth backed silver stuff that sticks like nothng else) to comfortably cover the area. (So placement was simple and rapid)
Last choice is plastic..........some bees go through them just fine, others will not cross them and will swarm rather than work through them.
When you have compromised ventilation channels, as in the common BS sytem of Hoffman broods below the QEx with Manley supers above, then framed excluders are more important. The spacing is required for the air flow. If the bee space is compromised it can give issues, and with wooden hives and their shrinkage and expansion especially in old pine and home made units, zincs, unframed, are a potential problem.
In poly however the bee space SHOULD not be an issue, just so long as you keep to one type of setup. Traditionally in Langstroth and Smith this is a full bee space at the top of the box, and none at the bottom. Using one size of box and frame pattern in poly (which we do) then the bees transit through the excluder is almost entirely up and down continuous channels, and then the zincs, unframed, are every bit as effective.
Last month in Denmark I was shown some serious issues through one maker trying to get smart. All the boxes in the two outfits I saw were to a standard pattern, albeit from a range of makers. Top bee space Lang deeps. Unaware of the issue, one of the outfits bought a full truckload of boxes in from another maker, only to find that they had subtly changed away from standard spec to half bee space at top AND bottom. Beekeeper, rather than punt them back, thought it would be OK, no big issue. It IS an issue. Bee space and a half some places (LOTS of ladder comb).......half a bee space in others (combs practically welded together with wax and propolis). Then at the top of the hive, instad of the full bee space under the flush fitting roof or feeder (no recess for bee space) you can find only half a bee space...............lots of cleaning to make things sit down, and bee crushing between the upper parts and the top bars..........messy.
Came back to add this bit.........the opinion that it IS an issue was the Danish beekeepers, not mines. He showed me the mess it had caused him. I was a bit surprised to be honest at the junk the bees drew in the space and a half.