Krark, the Thumbless

If something refers to your commander while you have two commanders, it refers to one of them of your choice. If you are instructed to perform an action on your commander (e.g. put it from the command zone into your hand due to Command Beacon), you choose one of your commanders at the time the effect happens.

If you copy a spell with targets, the copy will have the same targets unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for any of the targets, you can't choose a new legal target, that target remains unchanged (even if the current target is illegal).

You can choose two commanders with partner that are the same color or colors. In Commander Draft, you can even choose two of the same commander with partner if you drafted them. If you do this, make sure you keep the number of times you've cast each from the command zone clear for "commander tax" purposes.