Can i run 2x 140mm fans and 1x 120mm fan off a 1:3 fan splitter?

Solution
Yes, you can. More than three PC fans should use a powered hub or controller. It is also dependent on the fans. Most fan headers are limited to about 1 amp.
I've used splitters for two and three fans . The fans don't draw any more power at startup. In the Bios, you can set the RPM of the fans. Based on that setting it can be up to 100% at startup until the operating system loads. Then motherboard utility application takes over the control of the fans (with whatever temperature/RPM ramp that has been set).

That is why the fans often are loud at startup.