I have a cassandra cluster with 5 nodes that is using EC2 snitch but for the new node I want to add I want to use GossipingPropertyFileSnitch. Is it okay to have this node with a different snitch, will it cause any impact to the schema or schema versions?
All nodes in a cluster should use the same snitch since it is critical in determining the cluster topology and position of the replicas (to avoid them all being on the same rack for example.).
Just as an experiment, I changed a node in a 3 node sandbox cluster to use a different snitch and while it did start up, when running nodetool status on the 2 nodes with different snitches, they reported very different topologies - as you would know, this is not a good thing at all.
If you wish to move the whole cluster to GossipingPropertyFileSnitch, then there is a documented process on how to change the snitch of a cluster: https://docs.datastax.com/en/dse/6.8/dse-admin/datastax_enterprise/operations/opsSwitchSnitch.html
You will find that there are versions of that page for different versions of DSE. You would change the snitch first via the process, then add the additional node.