Your song's BPM setting (1/Cd on the Song's GLob page) flows through to the tempo of many things, from LFO speed divisors to the delay effects; a change in BPM will never throw off any tempo-based aspects of your song.
Everything syncs up throughout the synthesis engine, pattern playback and song mode. This makes your songs sound like well-planned, evolving pieces of music. Sync-locked LFOs can help with subtle build-ups, textures and "ear candy".
Settings that govern tempo (such as LFO rates) or length, often have their settings expressed in terms of quarter notes ("qn" or "q") or bars ("b"). A bar is 16 quarter notes.