I’m no expert so please don’t take my statements as fact.
You are right about the TN vs IPS panels, from my limited experience IPS in that price range isn’t worth it while you can get some pretty good TN for that price.
HDMI 2.0 can support 144hz but that both push up the price and isn’t really that important for a game like WoW (but really worth it in general). I THINK 1060 can run a 144hz screen through HDMI 2.0. Look it up.
A lot of people I know really like 27" screens and I bet it’s awesome for WoW, personally I use a BenQ 24" XL2411 (which is pretty old right now) which I am really happy with. The later version of these are unfortunately a bit more pricey and go for about 400£.
If you prefer to get something a bit cheaper look up AOC 24" LED 24B1XHS, I use it as my second monitor and it has a really streamlined design and I’m very happy with it in general. I got it for only about 120£ but you can probably get something way better for 200-300£, but it’s good