AMD Ryzen 7 7700X + MSI B650-P Pro MB + 32GB G.Skill Flare X5 DDR5-6000 Memory Expired

I had really crazy slow boot, it was a solid 30 seconds to even hit BIOS with this combo + m.2 drive. I ended up returning the whole thing.

I had really crazy slow boot, it was a solid 30 seconds to even hit BIOS with this combo + m.2 drive. I ended up returning the whole thing.

Ddr5 memory training initially but enabling memory context restore in bios thereafter should alleviate that

basically with am5 especially:
go ahead and make sure bios is up to date
enable memory context restore

12900k combo is $30 more. Passmark is about 15% higher 41 vs 36 on the intel. Or is the 7700x have other advantages?

The bios upgrade and enabling memory context restore suggestion is spot on. I picked up this bundle when it was $350 and did these exact things and have had no issues with boot times.

Those who purchase may also want to research making changes in the bios to undervolt to negative 30 on all cores. doing so dropped the cpu temp a little over 10c when running cinebench test and actually improved the score.

I don't think it's a good idea for you to recommend a -30 all core curve optimizer undervolt. If you get insanely lucky and win the silicon lottery it's possible to get a cpu that'll do -30 all core stable, but that's far more the exception than the rule. For the vast majority of zen 4 cpus there will be at least one core that require a significantly lower offset to be truly stable. There's also tons of other factors that play a role, like temperature and the clocking behavior of the cpu which can vary by motherboard and bios version. It's very easy to set too large of an offset without realizing, only to have minor instabilities you barely notice keep happening until all of the sudden your OS is corrupted and you'd better pray you have a full backup. It's also important to note that many of the earlier zen 4 undervolt results were back when agesa wasn't properly limiting voltages for cpus when expo was enabled.

For example, on my personal system with a 7900x and motherboard default cpu settings (excluding curve optimizer), I can set a very large all core offset in bios, boot into windows, and run benchmarks like cinebench just fine. However, my system is not stable. In fact, even at a -15 all core offset, I get errors on a couple of cores doing core cycling with small dataset sse instructions in occt. Meanwhile, at a -13 all core offset there are no errors on any core, and this was verified with a variety of occt tests, core cycler, y-cruncher, and prime95. While core cycling stress tests are a worst case scenario, any cpu errors whatsoever mean your system is at risk of instability and OS corruption. It's possible to use an unstable system without major issues, many people who undervolt do so (knowingly or unknowingly), but it's important to weigh the risks and benefits.

The general community consensus I've seen (in forums where people are actually properly testing their undervolts rather than random reddit threads) is that unless you get extremely unlucky practically all zen 4 cpus should be fully stable with a -10 all core offset. Anything beyond that comes down to the silicon lottery, and how much of a risk you're willing to take with your system's stability.

I had really crazy slow boot, it was a solid 30 seconds to even hit BIOS with this combo + m.2 drive. I ended up returning the whole thing.

12900k combo is $30 more. Passmark is about 15% higher 41 vs 36 on the intel. Or is the 7700x have other advantages?

I may be out of date, but dont intel CPUs usually run hotter and more power than AMD CPUs?