I've not had the time to test Godot as I am currently involved in several projects, both work related and otherwise. Once I clear my plate a bit more, I plan to dive in.

Having said that, I would guess (and it is only a guess) that Godot would probably not perform as well as Unreal or Unity. But if that ends up being the case, I'm OK with that. Godot, for the most part, is a pretty well-rounded engine made for both 2D and 3D games. It's roots in 2D are very apparent, especially since v2 kind of had 3D as more of an "add-on" then a full feature. V3 changed that, though.

So, with Godot, we have a game creation tool to create most every game you could want ... and get it to just about any platform, too ... all for free. And if a part of Godot does not perform as it should? Well, it's open source. If you're a talented programmer, you could make improvements where you need. Neither Unreal nor Unity offer that ability.

Most of us are not going to create some massively online player game with zillions of polys for environments and characters. And if we are making things work in 3DGS, then we should have no issues with Godot's 3D. As you pointed out, the ceiling should be higher in Godot than 3DGS.

In any case, I am excited to find time to learn this engine. It looks like it has a lot to offer. And glTF support means I should be able to get more out of my 3D program and into Godot as simply as possible.