The setup is feasible with the exception that I would recommend getting one Xpro-N Trigger instead of 2 Xpro-C (C is Canon, N is Nikon).

While it would not matter for purely manual flash, as only the middle contact is used for this, you then could use TTL strobes later on with the correct transmitter variant for the camera.

You do not write the size of the softboxes, I would recommend rather getting one 120cm round or octa and two strip boxes. With softboxes: the larger the softbox relative to the subject, the softer the light. If you have the room, bigger tends to be more versatile.

The SK400II has a built in radio receiver that works with the Godox Xpro, no coupling is needed. Just the correct channel and group.

If you get the Walimex background system with levers instead of wing-nut-like fasteners, you will notice that they become loose with use. A small tip would be get a cheap pack of Manfrotto large plastic cable clips. They, by sheer coincidence, have a side that is the right-sized key for refastening the levers. And they click to the stand, so you always have them at hand.

I would also recommend getting some cheap sandbags, as a big softbox tends to need some weight at the base with light and cheap light stands.

Speaking of those: They are rated for 1.5 kg max weight. That is the flash head without any softbox. You might want to see if you can find stands that are rated for a bit more weight to offer a stable platform. I recommend looking for used c-stands, if you can. They are forever. The Walimex Pro stands with wing-nut fasteners are ok-ish for the start though and also cost about 30-40 dollars.

I started with a similar setup, just not with SK400II, but 2 AD200 and 1 AD600BM. They are more expensive but also more flexible due to battery operation. However, the mains powered ones usually have better recycle time.

A budget tip: If you do not plan to have complete control over your light and are not doing mainly low key photos, umbrellas are a dirt cheap and fantastic alternative to softboxes. They produce similar light quality, but are bit less directed and you have more light spill.