I built a couple of PC's, one for home one for work during last summer. Both based on ASUS PRO Q470M C/CSM motherboard. No good for overclocking, but does have the all important on-board serial and LPT ports and old school Dsub15 video output :-) One is running an i5-10600K, and the other an i7-10700.
There is no point buying the 'K' version of anything unless you're intending to overclock. They just get hotter, and need bigger CPU fans and more powerful PSUs. I only bought the i5-10600K because it was being offered at the same price as the i5-10600, and the minute I realised I needed a bigger heatsink (K chips don't come with a heatsink!) I got buyers remorse.
The i3/i5 have a maximum memory frequency of 2666, whereas the i7/i9 can use 2933. Again, no point in paying extra for memory faster than your processor can support, unless you're going to overclock. I'd also be cautious of buying memory faster than you really need because you're then relying on the memories SPD definitions to support the speeds you can use. If it doesn't then it'll drop down to an even slower speed, and you'll have to poke about in the bios to get the speed you want.
I've used ADATA XPG SX8200 PRO m.2 PCIe3x4 SSD's - Intel chipsets don't support PCIe-4 yet.
The biggest thing I've discovered is that unless the applications you're running are new enough to exploit the number of cores or threads the processor has, you're just wasting money on more cores. Single threaded apps run on a single thread/core, and won't any run faster if you run them on a multi core processor (excepting the slight improvement in that OS may exploit other cores). What matters for single thread apps is single thread performance. Also, not all cores are equal - typically two or three of them will boost to higher frequencies than the others.
I don't do gaming, so on-board graphics is all I ever use. However, be aware it's almost impossible to get Windows 2K or Win7 to run on anything after Gen-8.
The 11th gen CPU's when they do come out will have fewer cores than the 10th gen. They're promising faster single core performance, but the multicore performance is only marginally better.