Yes, the channels are reversed from the normal on other amplifiers (left on the left when facing the FRONT of the amp has become the norm). But if you just follow the labeling on the amp itself you will be fine. Use the balance control on your preamp to verify. Also if you use a streaming service search for test tones. They usually have a left channel / right channel signal you can use to verify.
Regarding power level at 4 ohms, I have Caladans which are 4 ohms. My other amp is an AGD Tempo (100w at 8, 200w at 4). The S5.5 plays louder than the AGD does for the same preamp setting. I don't play music really loud, so maybe the 5.5 clips sooner, I don't know. But it is hard for me to believe that this thing runs out of steam into 4 ohms under any but the most extreme circumstances.