Tcv = turbo control valve or
Bcs = boost control solenoid
Bcs on early 850 turbos, tcv later turbos and a better design.
Both these controls the boost via the ecu so it determines when the boost comes in and how hard according to the map on the ecu therefore protecting you from bending rods and boosting too high.
MBC = Manual boost control, you set the boost top level and that's basically it, it comes on boost as soon as you put your foot down, more pressure on the loud pedal = more boost up to the level its set to.
If you floor it under 3k rpm you are very likely to bend a chocolate rod, it's easy to do especially with an 18 or 19t, you need alot of self control or forged rods.
However they are a lot of fun and I've run one for years ?