I have built enterprise networks since the early 90’s, you will not have any problems using cat5/e cables for a 1G network. If you have issues with cat5, check each cable to make sure it’s terminated properly by using a Fluke meter.
Also, you don’t need a dedicated streamer, just get a dac with Ethernet and put roon or audirvana on a Mac mini in a room outside of your audio room. The only reason to get a dedicated streamer is because your dac doesn’t have Ethernet or you want to use the best connection to a dac and that’s i2s.