It really depends for me. Sometimes I have so little clothing to wash that everything goes into one load. I usually sort by underwear, darks including jeans, socks and dark shirts. If I have just a few light things, they sometimes go in with underwear. Sometimes, to help make my loads a decent size, I will add my robe or a blanket or something large to help fill it out.
I purchased a new washer and dryer last fall and I wanted a large tub so that washing blankets, quilts, etc., would be easier. The tub is an impeller, not an agitator. It provides a larger washing space. It uses little water this way. There is also a dispenser for detergent and fabric softener, so for the first time in my life I can use fabric softener without having to stand there and wait for the rinse to add it. It has many bells and whistles as well, including self regulating filler. It is a top loading machine. I have used a few front loaders while house sitting and they all smell bad. I almost always use my dryer to dry my laundry, but bras and a few other things get hung to dry. The new washer has setting for how dry to spin the clothes. This really helps in the dryer phase.
Laundry detergent: I have used powdered laundry detergent for years. When I worked with someone who sold Amway, I always purchased from them. After I purchased my new machines last fall, I found large bottles of Ecos laundry detergent at Costco It says that it is plant based. I thought I'd try it, and I really like it. I pour a little into the dispenser and the washer dispenses when it want to.