It should detect out of the box even with a G1840 although I suggest a better processor like a minimum of G3240 and a recommended corei3 4130 which are almost same price with G3240.
Windows 10 Pro is the best for mining, if it doesn't detect out of the box enter in Bios change anything like PCIE slot and after the restart it will detect automatically.
My personal experience with this board is that it recognizes automatically the cards, at least that was my case with 6x RX 570 8GB Sapphire Nitro.
Thanks.
Is CPU a showstopper? Reason asking is that
I have a bit old CPU (not remember exactly which model). And in my part of the world its already pretty hard to find the CPUs for this board.
In Nicehash the G1840 it will run slow and sometimes crash, other than that if you use directly Claymore, EBWF it will work normally. I suggest go with minimum G3240 which is about 50-60 USD new and a lot less used if you can. It is not a showstopper.