I'm tech guys, expert in switch/routing field, i will try to use general word. It will change nothing, the switch just orientate the data from a point A to a point B without modifying it, it's just for orientation. This replacement is certainly to anticipate congestion at the aggretion point. Network work with oversizing, we rarely overload the local network, it's design for it.
The transition time from the server to your pc will not variate or maybe be variate by a 0.001% but the save time it's all about the server of UO, it's the time the database need to copy/compress information to a save place.
The database type and power of the server and storage type(hard drive or SSD) will influence grantly the save time. UO is an old game, i don't know if it's possible to optimize more this process as we already have a war machine server, it's was not designed for it