I have got the Samsung Galaxy S8. Runs perfectly on the highest settings. The S8+ and Note 8 just have a bigger screen and battery (the Note has 2 GBs RAM more but 4GB is also enough). So if you like bigger screens go for the S8+ or Note 8.
But if you want an even better performance, wait for the S9. It has been announced on Sunday and it will launch in March. This phone has a new processor which is said to be 30% more powerful than the processor of the S8.
If you have enough money, go for the S9.
Another point: The Note 8 and the newer S9/+ have got a better camera than the S8/+. Keep that in mind.
But my recommendation: Go for the S8. Not too big, not too small, awesome performance and design. If you buy the S8, you still have got money to buy other things for IF/other stuff.