B3 differences
You need to differentiate between B3 models. There are three different engines as the aircraft has developed. The 2B used the single channel Fadec the Off/Idle/Fly Fadec switch with manual control of the engine via twist grip if there was a Fadec failure. The 2B1 introduced a dual channel Fadec with mechanical back up and an Off/On switch with idle and flight controlled by twist grip positions. The 2B1 models also offered the IGW to 5250 if equipped with dual hyd. The newest B3, marketed as the "B3e" but still certified as a B3, offers the 2D engine with the same IGW with dual Hydraulics, same Off/On switch with idle/flight controlled by the two position twist grip, dual channel Fadec with mechanical backup, an improved Fadec, longer MCP of 30 min and an eventual engine TBO 0f 6,000 hrs (4,000 as of now). With the dual channel versions there is no "manual" control. If both independent Fadec channels fail, there is a mechanical back up but no manual backup. I'm not a 10,000 hr guy but have time in all three versions and the emergency procedures are significantly different between the 2b and the 2B1/2D as far as fuel control/Fadec failures.
The B2's do not have Fadec and the vast majority are equipped with a fuel flow control (FFC) mounted on the floor. A twist grip is available as a factory option although not very common and very pricey. With the twist grip option, the start is completely manually modulated similar to RR C30 in the 206Ls and MD530s. On the newest B2's, there is an "idle stop" incorporated in the throttle quadrant (emergency shutoff, rotor brake, FFC). Up until 2013, this was not offered and there was no "idle stop", you had to watch Ng to know where idle was (67-70% Ng) and, in emergency procedures/auto rotation training, make sure not to move it too far to the rear as to cause a shutdown. In a hover, a tail rotor failure in a B2 with a FFC would be very sporty. Letting go of the collective to grab the FFC, pull it out of the detent, shut the engine down and then grab the collective again to cushion the landing all while you are trying to keep the thing from spinning too fast before the skids contact the ground and you roll over? I would guess the "average" pilot couldn't do it all in the real deal, myself included, especially when you figure in the time to recognize the actual problem as you start to spin. In training you are expecting it but of course you are not in real life.
Regards.