Traditional vs Roth depends entirely on expected marginal rate in retirement. If you expect to have a higher marginal rate than 12% and lower than 22% then you should recharacterize the amount that puts you right on the line between the 12% and 22% brackets. Remember to consider current vs future state taxes and ACA subsidies.
What Terran said. And it's not all one or the other. We needed $2k in Traditional to get into the 12% bracket so I did that, then put the remaining $10k in ROTHs