How long can you wait? The point of my many posts here is to tell you that if you can wait a few months, you can pay for an i5 and get the performance of the 2017 i7.
However, if you buy now, you'll get a significantly slower 2017 i5 machine for that price.
I see, thank you for your advice! I'm thinking of waiting until around November to see if they release the new iMacs. If they don't announce anything new for this year, I hope to get a better deal on the 2017 iMac.
[doublepost=1529513299][/doublepost]So the information I've gathered it would be best to:
plan A: wait a few more months and see if they announce new iMacs for 2018
plan B: get the 2017 27" i5 3.4GHz with 256SSD (would that be enough?) instead of an i5 3.8 with 2TB fusion drive even if the 3.8 is cheaper? Regarding RAM I will go for 8GB and upgrade it myself to 16 or 24 GB.
I think your understanding of AMD's product line is far too rigid.
As mentioned, Vega is not just two chips. It's an entire generation, but it just so happens, not all of the versions of Vega are out yet. Vega won't just get different clock speeds either.
In terms of RX, Apple is already using RX 500 series, albeit with their own configurations binned with power characteristics appropriate for the iMac, and then rebranded as Radeon Pro. I should also point out that AMD actually advertises the RX chips for mobile use. And RX 500X is mainly just a rebrand of RX 500, which Apple is already using. If Apple were to use Polaris RX in 2018, then it'd probably just be named Radeon Pro 500X series.
Or else they could release later on with Vega, just not the same Vega that is in the iMac Pro.