Definitely the G303. Avoid the G502 if you plan on playing both Overwatch and CS:GO due to its weight. The G402 on the other hand is just outdated and there are better choices out there. Those mice aren't really as good as the G303 when it comes to FPS, even osu.
But to be honest if you plan on playing with fingertip grip, just get a Logitech G Pro, Zowie FK2, or the Nixeus Revel. I own the Nixeus Revel and the Logitech G102 (downgraded version of G Pro) and both are amazing for finger tip although I'm more of a hybrid grip player.
lethal_osu wrote:
The G502 Proteus Core is an amazing mouse. You can freely customize it's weight to your liking, and the grip is phenomenal.
The weight of the mouse without the weights is 125g, if I remember correctly? Way too heavy, like a brick.
TakuMii wrote:
How about the G102? 
It's what I own and I can definitely vouch for it. It has a rubber cable that isn't stiff and is comparable to Zowie cables, better than braided cables. Its sensor and mouse 1/2 are downgraded, with the sensor not being the PMW3366 (it uses a Mercury sensor which is not that far off) and the mouse button having 10m click lifespan compared to the 20m. It's only $20 here though compared to the G Pro's price tag which is overpriced considering the G102 exists at $70, and I'm sure you can get one at eBay with the same price + shipping fees.