If you are basing that on the current GPU's that are available on the market... Just be advised that next-gen consoles are using RDNA2 which will come with a 50% performance-per-watt improvement over RDNA 1/Navi.
Not really. Faster Ram doesn't mean you have more Ram available.
Possibility exists for a 256GB/512GB variant which will rely a little more heavily on aftermarket expandable storage that Microsoft can profit from...
7.5 GB of usable RAM vs 9 GB of usable RAM, yes they are roughly on par. Let's not forget that the very same games run on PS4pro with only 6 GB of usable RAM as well as PS4 with a mere 5.5 GB.... The only difference is usually the resolution and texture quality. Well a 3 GB of difference between the PS4pro and XBX creates a difference in texture quality but a 1.5 GB will not, but merely resolution differences, which is why I am not so certain that Lockhart can run all XBX games at 4K resolution but will not have a problem running them at 1440p generally speaking.
RDNA 2 is roughly 50%+ faster than Polaris, but of course things vary; however, in the general scheme of things, pretty much 2020 and earlier games should run similarly, if not better, on Lockhart, than in XBX, even if they need to be scaled down to 1440p for one reason or another. In the next-gen compatible titles, however, it will be more performant than XBX due to use of faster RAM, faster SSD, and the utilization of the faster CPU.
Finally, to address some of the suggestions here, the price gap between XBSX will be around $100-$150, depending on what is included in the configuration. If it comes as a digital only console, we might be looking at a $250 4TF 10 GB Lockhart vs fully-fledged $400 XBSX (or for $350 and $500 respectively), which makes even more sense, competing with a regular $500 PS5 and a digital only $450 one, which will then make the competition very interesting between the two. In such a scenario, PS5 will still win in all Asia, and the non-English speaking world, while the English speaking would be home to a fierce competition.