Storage is still the worst bottleneck on pretty much every machine. Get a SSD or SSD/HDD hybrid, get enough RAM. CPUs get less and less importance these days. Having more cores will likely not help much, as software sucks. Having more parallel applications means more pressure on IO/Memory.
In general, while it is not a popular opinion, I suggest getting a latest-gen, best cpu iMac, with no upgrades except for a fusion drive and then maybe at some point additional RAM. When not being in the "PC Masterrace, ultra graphics + enhancer + 4k + latest gen" group, that's enough for everything, even gaming.