Please help having trouble finding a liquid CPU cooler: https://au.pcpartpicker.com/list/288nr6
Why you don't mount an Air cooler?
I just don't know how big I can get it I know for a fact that it can fit a 240mm liquid cooler
PCPP is actually pretty clever and should only show you coolers that are compatible with you build when you go to edit it/select a cooler, but if you wanna confirm how much space you have you can go to the case manufacturers website, or if they don't have it there (which is unlikely but I've seen it happen) check some case reviews from the usual tech sites and it'll prolly be mentioned in one of them.
What ones would be good do consider if I went air cooler
This one from Be Quiet!
will this be better than the water cooler?
For an 2600X, it's more than enough to keep it decently cool. :)
Corsair H110i, NZXT Kracken, or really any other 240 mm rad are good options.
Use the H100i, there are some builds using it