I assume you're talking about "Freedom of the Hills" and the belay set-up where you use the climbing rope to clove hitch into your anchors. Â I almost always do that when climbing alpine ice. Â You don't have to carry as much pro that way and it seems faster. Â It's usually done with a double rope system so you have redundancy in your tie-ins, but it can be done with one rope as well.
The disadvantages of that type of anchor is as you pointed out, it isn't equalized. Â And if you are swinging leads, the anchor may be fine for bringing up your second, but it may not be adequate for protecting a leader fall, particularly on vertical ice.
Craig Luebben's book "Climbing Ice" advises that three screws should always be used by less experienced climbers. Â More experienced climbers can get by with two screws in good ice. Â Everything is so variable with ice, so it depends on the quality, density, temperature, depth, and solidity of the ice. Â
As a side note, BD and Luebben's tests determined that the holding power of ice screws comes from the threads. Â If you compare a 17 cm to a 22 cm screw, the thread length is identical, so in good ice they should be equivalent in holding power. Â The exception would be with alpine ice where the outer layer is often crud and the extra length of the 22 cm screw helps penetrate down to the good ice.