Generally speaking, is there a way to assign a public IP address individually for each server to be used when SFP+ port delivers internet with /24 pool of IP addresses directly to the switch, and the switch connects to the servers straight away (as for example on Ubiquiti Unifi Switch or their Edgeswitch)
You do need some kind of routing.
If you advertise your own /24 prefix / AS a router is required as gateway.
The uplink subnet is different from your /24 subnet, so a router is required to forward between those networks. If you bridged your servers directly to your uplink they'd require a gateway for their default route. Also, the uplink peers would be required to talk to the server IPs directly on the wire which they likely won't do. If you can't use someone else's router you need to provide your own (your external provider could provide that).
Also, bridging your servers to the uplink would potentially expose their internal communication and may expose them to L2-based attacks.
As a bare minimum, a layer-3 switch would work, shutting out L2 attacks and providing routing both ways. At the very least you should carefully configure ACLs on an L3 switch to block obvious L3 attacks. Using a firewall provides better protection, so that should be preferred.
If I understand the question - you have three servers on the same subnet, connected to the same switch - that's fine, traffic to the subnet will be routed by the provider's router, and arp will take care of delivery of the correct address to the correct server.
In other words, the router port at the provider and your three servers are all on the same subnet, there's no need for a router between them.
