Out of the box? Probably, as Ubuntu doesn't come with everything you need for gaming, so it doesn't work at all. Once you install all the same packages I imagine it's about the same. Usually a distro isn't doing anything particularly special. It's mostly just a collection of packages, which you can install on any other distro as well.

Word on the street is that Ubuntu gets updates very slowly. If people want latest and greatest drivers kernels etc then fedora and its spins is the way. Or arch if you are into that sorta thing.

no

No

If using steam gaming mode by default with deck/htpc variant. Yes, as it doesn't even boot up an ~~OS~~ Desktop Environment in the background. It's not going to be much more but it's a non-zero amount that will felt more or less depending on the innate power of your hardware