Mixed ohm ratings & do you set the ohm ratings?

Hi, I’m pretty much a total newbie when it comes to ICE. Recently I bought myself a pair of Infinity kappa 65.7cs components for my cinq to put in some custom door pods. These speakers are rated to run at 2Ohm.
I intend to buy a 4 channel amplifier of around £100 budget to put under my drivers seat and a slimline Pioneer 12” woofer for my wheel well.
I've heard you have to run a sub at 4ohm, I could bridge the rear connections to get the power.
What I don’t know is how is the Ohm rating set? Is it just dependant on how the speakers are already configured to run at or are there controls on the amp or a way of wiring them?
Basically, could any 4-channel amp run a mixed ohm 2.1 setup using 2Ohm fronts and 4 ohm powering the sub?

A speaker's ohmage is 'set' by the voice coil configurations on the speakers, e.g. a 4ohm single voice coil (SVC) is designed to take a 4ohm current. A dual voice coil (DVC) speaker can be wired to 2 different impedances, e.g. a 2 ohm DVC can be wired for a 1 ohm or 4 ohm load, a 4 ohm DVC can be wired for a 2 ohm or 8 ohm impedance. So with a DVC speaker, both the voice coil configuration and the way it's wired can affect the ohmage it runs at .
You should be able to run a 4 channel amp with 2 different ohmages, e.g. 4 ohm on the front channels, and 2 ohm on the rears No doubt I'll be corrected if I'm wrong

I don't know if these speakers have are DVC, I guess they are 2 Ohm SVC.
Bascially; if I wire them up to an amp the usual way, the amp will run them at their rated 2 Ohm anyway? or does it provide 4 ohms by default and I have to wire the speakers appropriately to produce their required 2 ohm value?

They're 2ohm single voice coil.

Make sure the amp is 2ohm stable (99.9% are) and wire them up as normal. Low impedance loads usually increase an amps output, so if you're amp is rated at 50wrms @ 4ohm, it could do anywhere upto 100w @ 2ohm.

DONT'T bridge the amp to a 2ohm coil unless it's 1ohm stable (which few are).