Is that okay or will that damage my hardware? Because I just got a new power supply (corsair vs650) with a 8x plug but my motherboard (h81m-plus) only has a 4x plug
Is this fine or am I out of my mind?
The connectors on PSU's now are often 4+4 CPU connectors now. They should look similar to the following:
The manual for your PSU states:
B. If your motherboard has a four-pin socket, detach the four-pin from the eight-pin cable, and then plug this four-pin cable directly to your motherboard.
Be sure you're using the right connector, there are other 8 PIN connectors (Often PCI-e 6+2 pin). You are likely using the correct one as they should only fit in the correct sockets, but double check for a splitable connector as pictured.
This video shows what looks like the correct connector at 3:25.