4-3-3 is a very hard formation to play. You need players that have great stamina and work rate. Coleman will be good in this formation along with Gana, Sigurdsson, Klaassen and Walcott (good work rate). Also Davies could do a job here along with a fit James McC.
The likes of Lookman and Bolasie will not be good here as of now (Bolasie probably never, to lazy) Lookman works not good enough on the defensive currently (he might get this going under Silva if given a chance). Niasse will be better in this formation than Tosun just because of work rate and pace (so important in this 4-3-3 formation in my opinion)