Noob Question About Wii to receiver, assignable inputs, etc.

Hi guys, brand new user here. Hopefully this is not a question that's been asked a billion times, or is stupid.

I just ordered a Yamaha RX-V567 receiver, and after ordering realized something that has me slightly nervous/annoyed. The component inputs on the back only have coax and optical audio inputs, meaning there's nowhere for my Wii component audio cables to plug in.

I know I can still plug it into the TV and do audio from there, but I was really hoping to streamline all my inputs into the receiver (that's the point of having one right?).

I know my receiver has "assignable inputs," but I haven't tracked down a definition for what that means exactly. Does this mean I could plug the video cables into the component slot (AV1) and then plug the audio cables into a different analog slot (AV4) and the receiver would pull the video from AV1 and the audio from AV4 into one channel?

The receiver can also do HDMI 1.4 for two way audio, but my TV is only HDMI1.3. I'm assuming that means the TV would not send audio back to the receiver and I need an optical cable to do that. Am I understanding that correctly?

Any and all help is appreciated!

thanks for the reply!

Followup question:

Given the amount of retro games I play on my Wii, input lag is seriously important to me. Do receivers like this automatically upscale the image? Will I be able to bypass that processing in the settings? With the Wii the input lag is barely perveivable with my setup right now - I really don't want to add extra processing to slow things down there. I'm assuming if it is a problem that I could just run component from the receiver to the TV to bypass this processing?

I'm assuming that if I let the receiver send the data through the HDMI cable it will automatically upscale.