Can you use an Ethernet cable (Cat6) in a switch's SFP+ port to connect to another switch?
An SFP(+) port requires a PHY module unless it's used with a direct-attach cable (DAC) that has fixed SFP+ modules at its ends.
Not all SFP/SFP+ ports support 1000BASE-T modules. Quite a few SFP+ ports don't support 10GBASE-T (and if they do the reach is normally reduced to 30 m or so).
In any case, you'll need to check the device documentation for compatible modules. Most vendors also try to force you to use "original" modules, so you'll make sure the module at hand shows the required brand as well.