You don't normally need resistors.
Genuine seats have built in resistor packs so you can plug them straight in.
The airbag plugs can be different. Although usually you are fine as you just need to trim a part of the clip to make them fit and disconnect fine.
My R32 buckets did have a connection, but it's different from my standard GTI's one so I needed the resistors. You can buy them for about £2 each on eBay, just make sure to get the right resistance!
The ones you need are 2.1ohm from Maplins, around 15p each... know maybe it's nice to have to lack of worry and the cost is small but it's the principle haha.
Yeah the seat plugs can be different.. depending on which way you only need to trim a small bit of plastic off the clip itself .. my Recaros are from an S3 and fitted straight into my Golf, however the plug on the Scirocco was slightly different so we had to trim a bit of non-essential plastic, and they work fine.. The Scirocco seats in the Golf were a bit harder but again only needed trimming of the plug.
And wire them in like this.