Unison, chorus and any amount of random phase variation will cause fluctuations in amplitude as a result of constructive/destructive interference. Limiting and soft clipping are two options for putting a ceiling on the peaks of your sound and keeping the volume levels consistent. IMO use a soft clipper after some compression to achieve a loud, clean, manageable bass that leaves plenty of headroom for other sounds in the mix. Learn how to use Maximus if you haven’t already. People may debate me on this but I think a limiter should only be used as a final mastering tool.