Good stuff, all of it. Really depends on what you're trying to accomplish specifically, and if you're juiced or not. Obviously, dosing up the vitamin T levels will let you pull of high frequency AND high(er) volume.
I like using the frequency approach on the 2x a day schedule. Squat 3x a week, and use the other times for other body parts. Pick whatever you want to specialize on (if anything) and hammer it multiple times a week. Volume is dependent on juicing or not.
Although I've been pretty successful with moderately high volumes naturally when I'm in top conditioning, I would not recommend it for many people who are NOT juicing, because it's really unsustainable unless you're in really reaaally good condition when you start the split. But it's all individual anyway and different people can handle different workloads.
Example of something I used:
Day---AM training, PM training ---every repeated workout had different rep schemes or weight %s used (ie--all the dl workouts were different)
Mon--- Squat/DL, Chest/back
Tues---Olympic movements, isolation stuff (optional)
Wed--- Squat/DL, Chest/back
Fri ---- Squat/DL, Chest/back
Sat---- Oly movements, isolation (optional)
Only could hold that schedule for 2-3 weeks before breaking down, but after a rest week (still in the gym, very light stuff though), I made great progress in my key lifts.
Modified for something more bodybuilding oriented, I guess I would do something similar to this:
Mon---Priority #1, Priority #2
Tues---OFF or maintenance body parts (eg shoulders or whatever are your best aspects)
Wed---Priority #1, Priority #2
Fri---- Priority #1, Priority #2
Sat----OFF or maintenance body parts
maintenance body part days are meant to be easy on your nervous system and recovery capabilities. Just keeping enough work to not let them shrink.