I need to remove this metal conduit or at least bring it even with the floor. I don't need to worry about preserving the wires inside the conduit. I only have a little hacksaw, but I'm open to buying other tools if needed. What's the best way to get rid of this conduit so that it's even with or below the floor?
I'm assuming you don't have access to the backside of this conduit. If you did, you would just disassemble it - find the nearest coupler, uncouple it, and remove the pipe.
Remember to remove these orphan wires entirely; all the way back to the previous junction box (or past it, if they go past it). You're not supposed to leave orphan wires, though.
4.5" angle grinder. Pick one up at harbor freight for $15. They are so cheap I just keep 3 around with different thickness discs attached instead of fumbling to change them. If one dies you have spares.
The other tools - oscillating/reciprocating/dremel generally are going to be more expensive, slower, and harder to get a flush cut. While I tend to buy cheap grinders I don't recommend cheaping out on the other tools.