The IS200 is always recommended to have the 10w30, you will need 4.1 litres all up,
Always used genuine lexus *cough toyota cough* filters and they seem fine, so can't pass comment on the K&N ones, but I have plugged that part number into the K&N website and that filter is not for an IS200, will work in an IS300, SC430, RX300, LX470, LS430, GS430, GS300, ES300,
According to their site the only product they make for an IS200 is an air filter, i'm not sure if the IS300s filters have the same fittings but I know that the filter in the 300 is physically bigger (100ml bigger in the amount of fluid it will retain.)
HP-1002 Application List
http://www.knfilters.com/search/applications.aspx?Prod=HP-1002