The load needs to be on the drain or you'll blow the MOSFET (ie use the first circuit) - you want the on-voltage across the MOSFET to be as small as possible and the source-follower circuit (second example) cannot do this and will put loads of power straight into the MOSFET die and likely melt it.
The third example makes no sense - why do you have two loads in series?
If you want the load switched on the high-side then you need a p-channel MOSFET and a level-shifting circuit to drive its gate.
If using an n-channel as in circuit 1 you will want a logic-level MOSFET (or you'll need a level-shifting circuit too).
When selecting a MOSFET ignore the current rating, you need to get the Rds(on) resistance and calculate the power dissipation (I-squared-R). Try and keep the power dissipation low (or at least select an appropriate heatsink). All the current rating is is the maximum-power-with-infinite-heatsink rating - normally you don't go anywhere near this current since you'll be losing volts across the device.