Things get scratched because of the hardness or durability of the coating, not necessarily the color - though they will be more apparent/harder to hide with white. A good white powder coat should be pretty durable though.
+40 is best to keep suspension geometry as designed, but you could go up or down 5mm without too much concern.
Uhh pretty much anything Aluminum Cast is cheapest and heaviest and WEAKEST (the stock wheels), flow formed (sometimes called flow "forged" but that's a lie lol) is medium price and fairly light and then forged is most expensive and lightest (only a little lighter than flow form normally). Personally i'd suggest getting a pair of flow formed wheels to get the best trade-off between price, weight and strength.
Thanks much. Looking at websites I’m surprised that they don’t post their wheels’ material. I’m assuming that means that they are cast. Do u recommend any sites or chains for searching for forged wheels?