2008 RX400H driving in snow and check system came on with orange triangle on right and horseshoe with exclamation point on left flashing. Is this the tire sensors? Can I drive with horseshoe flashing?

Orange triangle is a "Master warning light", You won't know what it is until you check it with a code reader. Could be serious could be nothing you won't know until the code is read. Code readers can usually be borrowed from Auto parts stores for free, if you do not know how to use one ask them for help it takes only a couple minutes and should be free. Write this code down, erase it, then Google it to find out what it means (example - P0430). Type into Google your cars year, model, then the code it should tell you the problem and also lead you to this site where others have had the same issues and how they resolved it.
The horseshoe is likely your tire pressure warning - check all your tires especially your spares air pressure. Checking the spare tire is not fun but needs to be done annually (I keep my spare at 40 lbs PSI). When the weather chagnes up or down drastically it always quickly affects your tire pressures. As for spare tires, almost no one ever checks theirs for pressure or condition (my spare was in horrific shape with no tread and cords showing through when I bought my used RX)

If you do not already have a owners manual pull one down online for free.