Hey great question m8.
All 5-2-3 tactics in general are very good whenever you see that formation things usually work out very good.However I had came to the belief that the best 5-2-3 are the ones that use simple roles in the midfield and with the 3 advanced forwards. For example this: http://www.fm-base.co.uk/forum/shar...-scored-57-conceded-1-2-strikers-scoring.html
As far as countering 5-2-3 that is the most absurd idea I ever heard because theres no such thing as a counter to a 5-2-3.
The mighty 5-2-3 poopoo's on ANY other formations ..mind you there are some parody formations for example 5-2-1-2 or some kind of 5-3-2's that work alright but its well known that the 5-2-3 is the BEST and non counterable formation on 2018 fm.