[FiSheYe]

I think with the given information you provided here this is a bet. Now considering the stacksizes and how other hands went to showdown I either bet the 4k+ (depends on which amounts you consider the most suspicious) or shove. I really like shoving in that spot cuz you will be called with a frequency comparable to a big river bet but more overall benefits and it it's a beautiful board for Villain to make a hero call.
C/C is another option giving your opponent room to hang himself but I think this is a spot where he might actually call your shove almost lighter than value bet those hands here. Since you have the flushdraw I doubt he will have a draw all to often so the advantage to see a bluffbet on the river decreases. Imho shove > good sized bet > c/c..
With enough metagaming/reads and stuff this could be a c/r in certain spots as well (giving us a total of 4options). Obviously we need the right circumstances and a smallish river bet but it could be an option sometimes.