yes, but it is not really needed since all directions work (the cover must open under it the main engine is located)
A bigger engine usually has a better Specific Impulse, which means "more kilometers per liter". Attitude thrusters are not designed to have a good Specific Impulse, but to be very easy to ignite and cut off. The Soyuz TMA ones can do this dozens of time every second a bit like an automatic weapon (they have no "throttle", they are on/off and the computer manages those "bursts" duration and frequency to match the control inputs - we can't simulate that in Orbiter because we'd need a reliable framerate of like 1000 FPS, maybe in a few years! -). The Soyuz KDTU main engine (the center one) has 2 throttle modes (low and full), but it probably requires an ullage burn, so its "more efficient" BUT "less convenient".
Also the design plan is that, if for some reason the main engine fails completely, the small ones can be used as a backup. Even if they burn more fuel and don't lower the orbit as much as the main one, Soyuz is a LEO vehicle so it will be enough to bring the crew back on Earth in a reasonable delay through orbit decay (in the worst case cosmonauts have 48 hours of emergency supplies and even a small shotgun - anti-bear-gun - which they might also need on Earth in case of such an non-controlled reentry).
The other benefit of that "cross" pattern is that you can control pitch and yaw with those 4 engines only, that's some kind of backup if the DO (orientation system) fails. Robust design.