The specs for those relays is rather optimistic. The NO contact alone is rated for 15A 250VAC use, the NC contact however is rated much lower, typically 5A at 250VAC, as the closing of the contact is faster than the opening. Also using the relay to switch with a potential difference on the 2 contacts requires a different relay, you need one with 2mm minimum of contact separation when they are open, so that the arc created when it opens can extinguish, and you need to use another contact set on the same armature to do the normally closed operation, so that there is no possibility of the arc created during opening can be attracted to the other pole.
I use the same relays for 250VAC use, though only as a single pole switch. Doing a changeover will cause it to arc over between poles as the clearance is small, typically 1mm. You want to use a double pole relay instead, so that there is no way to arc over. Preferably a mains rated contactor, which has double break contacts so that even if one does weld shut temporarily the second one will still open, and the torque created during this will break the weld, while if it does weld shut totally it will not operate the other contact set at all. A little more expensive than the $1 relay, but will operate reliably for decades. You probably will use the single pole relay as a drive for the coil, as they typically do not come with 5V coils, typically 24VDC, 24VAC, 36VAC, 48VDC, 48VAC, 60VDC, 115VAC, 115VDC, 220VAC for the most common types.