It could be down to SSD speeds, better faster storage can make a system feel snappier. But because the Intel chip isn’t power limited, it can clock to the moon, just letting it get more stuff done per cycle. M1 is great because it gets close enough to that level of performance while sipping electricity and being portable

IPC is exactly the same between 12th and 14th gen. Its only the clock speed and number of cores that changes the performance

That sounds like a very high estimate for a head job. Take it to a mom n pop shop and get quotes, or just call around instead of taking it everywhere