To answer your question - you are straddling a powder speed range with your requested bullet weights in 223/308. CFE223 would probably be one of your best bets. Varget and/or TAC could also do this for you. I would just embrace the fact that you may need to get two different powders for a 55 gr 223 load vs a 168 gr 308 load. Even if the load works on paper, there are many other considerations to loading beyond just looking at a load guide.

The good thing about this is that reloading supplies are slowly becoming available, and you will hopefully have your choice of supplies soon. Good luck!

In 223/308, I have used H335, Varget, IMR 4895, and IMR 4064. All provided good to excellent results as long as they were paired with the correct weight bullet.