In Mario Kart Wii, when you play online, after a race points are calculated based on the results of the race. Are guest racers taken into account in this calculation; in other words does it matter if a guest finishes before or after me? If so; how is his/her impact on the scores determined?
Yes, Guests are taken into calculation online, they impact scores just like a normal player.
Me and my brother used to play MKWii online a lot, and when he finishes ahead of me, the points I get are calculated as-if a non-guest player finished ahead of me.
Yes. In Worldwide/Continental races, guests are considered to have a VR/BR of 5000 for VR/BR calculations.