Performance Questions

So we have wcf in our app and the client is .net 4.8 with lots of UI controls that may not port to .net core.
We also have a .net server with wcf endpoints. The client writes all its data to the server through wcf

I looked into grpc protobuf-net and it does a good job reusing the WCF contracts from what i can see, but because client is 4.8, transport is http/1, which is not good.

How does coreWcf move the data in a 4.8 client? We actually want to convert the server to .net core, so 4.8 not an obstacle there

How can CoreWCF handle cross domain security?

I am told that we are using certs to overcome in classic WCF, which is a pain.

Thanks