I know Napoleon's senate was appointed, but what about the lower house? Were there political factions like in the first republic?
Just taking your question about elections to Napoleon's Corps législatif, the French National Assembly describes the situation as having the final election decided by the Senate from candidates nominated from lower groups, themselves elected from even lower groups, eventually involving local citizens (men aged over 21).
This has been described as a cascade electoral system, but it was designed to secure loyal support for Napoleon. The process was supposed to produce a body which would endorse Napoleon's proposals without debate. In theory the proposals had already been debated in the similarly selected Tribunat but when Napoleon decided the process was not producing the desired efficiency of decision making, he instead turned to direct rule endorsed by plebiscites.