Up to you. DDR5 RAM is more expensive. You already have a RAM kit so even the DDR4 one i listed is optional. It's faster but a luxury rather than a neccesity.
Not really. Asus Prime boards are not the best and the B760 is a budget chipset. The z690 is a flagship chipset for the 12th gen Intels. Those boards are superior though they were pricier close to launch. Today prices have come down because the z790 motherboards are the current flagships, though their specs are not much better.
Anyway, the Riptide is going to support not only the 12400F that you've got, but it can also run a newer 14700, should you want to upgrade to it once it's price comes down. That is a more powerful i7 and probably the best you can buy today unless you have money to burn and an endowment to pay your electricity bills.
The 12400 is hardly a match for a 4070 Super. HP and Dell have a habit of selling powerful GPUs in mediocre systems that severly limit their actual potential.
One dead giveaway is the lack of any heat spreaders on the power delivery side. Even dirt cheap motherboards will have something to dissipate the heat, unless there's going to be no heat because the CPU isn't going to get the power that would allow it to generate any. Which is what is happening to your gaming performance.
You say you only care about gaming and your scores are poor. The reason is the motherboard which is not meant for any serious gaming. The GPU has to do all the heavy lifting, which it can manage but if the CPU also has to deliver, it will be restricted.
Even the CPU fan on that picture looks hopeless. The 12400 normally comes with a better stock fan.
You can read more here:
https://www.maketecheasier.com/what-is-vrm/
The memory kit isn't such a huge problem.
I know you're not looking forward to building a new PC, and i don't think you should. Just get a proper motherboard like the Riptide, and a new case if you must. The Montech isn't too expensive at least and comes with fans installed so you don't have to buy any.
A new power supply is needed but you will be glad to have it.
You probably don't want to do this much either, but you've hit the limit of your gaming performance and have no other choice than to put up with it or upgrade.
Reuse as much as you can. Without new RAM, the cost is under $300. And it will not only be unlocked, but you will have something to build on in the coming years, upgrade-wise.
Lastly:
- the 12700 needs a better motherboard much more than the 12400.
- 12400 is second from the bottom of the entire Alder Lake line up. It's not too bad, but it's hardly a flier. Also, define "plenty"? As you have seen from first hand experience, it's very game-dependant whether it's plenty or not
- AM5 being unreliable is rubbish and bordering on disinformation, and i'm more team Intel than AMD. AM5 is currently the ideal platform for gaming, though it is limited to DDR5.
- The problem with HP/Dell/etc. isn't so much the proprietary stuff, it's how much money they take to sell a crippled product. That they don't crash is not a virtue. They're not supposed to crash.
- They do have some very good models, esp. non-gaming PCs. And yes, being able to just plug it in without having to figure out which damn power connector goes onto which naked pin is a definite plus for anyone but those mad enough to actualy like building PCs.