tiger barbs are fin nippers, best kept away from anything which has long fins like a gourami in my opinion. as for rasboras it would depend on the variety as there are lots to choose from but as long as the tiger barbs are kept in a shoal they should be more concerned with the hierarchy in their own group and leave other fish alone.I personally am consider Black Ruby Barbs to put in my tank eventually when some of the platy I have are gone and I have Narrow Wedge Harlequin otherwise known as Lambchop Rasbora. I think they should be ok as these Harlequin shoal nice and move fast and there are alot of cover and hiding places in my tank.regarding numbers for your tank it would depend on what else you have and not sure on the size of your tank. I know mine looks quite full right now with the number I have and I know I could probably get a few Corydoras in there to mix up the sand and that will be my limit until I need to replace any.