What determines the "speed" of current-tech motherboards? [2021]
Things are much more complicated now. Performance is dependent on the total system throughput, where the slowest component counts.
Building a PC has also now requires much more knowledge and errors are easy to come by. It's more economical in many cases to buy a good ready-made computer, rather than build one yourself.
The best source for comparison of computer components is PassMark, where you will find all these benchmarks:
