Can I use a single type of capacitor for all decoupling ( 1uF and 0402 )?
High frequency behavior (ie, inductance or ESL) of MLCC caps depends on:


Package shape and dimensions
Mounting inductance (ie, position of vias, etc)
And number of caps in parallel of course


Capacitance influences the self-resonant frequency of course, but only has a very small influence on inductance, mostly through making the package bigger. 

The real reason to stick lots of caps in parallel between power and ground planes is to lower the inductance. In this case, usually small values are used like 10-100nF, because it's cheaper. This matters for a PC motherboard where you got hundreds of caps.

If you replace them with 1µF, it will cost a little more, but it will work just as well.

For DIY stuff, it does make sense to do what you suggest. Just get a hundred 1µF caps with quantity pricing, and off you go. Please note that the "1µF" is only with 0V bias though, and smaller packages tend to lose more capacitance under bias than larger ones like 0805.

Note: I am not covering the case where the capacitor self resonant frequency is used in the design.