New to Steam Multiplayer in Unreal Engine

Hi, I’ve been using Unreal Engine and C++ for a long time, and I’ve published singleplayer games on itch, but I’ve never had the opportunity to delve into multiplayer. I’m familiar with the basics of netcode and server/client architecture in games, but I have no experience with either Steam or multiplayer in Unreal Engine.

I’d like to try creating something using Steam networking in Unreal Engine, and I have a couple of questions that I’m struggling to find a detailed and specific answer to online, so I thought of asking here. First of all, what is the main difference between Unreal Engine networking and Steam networking, and why is it advisable to use the latter for publishing on Steam? Then, I wanted to know if Steam also provides a server solution or if external resources must be used for that. Finally, even without a Steam publisher account, can I test the multiplayer of my game? Thanks in advance!