Sykar
Arcane
At this point I think it's very barely possible to hit 30 right before the elevator fight if you do absolutely everything or get very close. It's not bloted by any means.styg already bloated oddity and allowed to reach max lvl before DC, or close.
As such limiting number of encounters sounds silly, especially with some of them not even giving oddity xp
The DOM only segments being exclusive makes some sense because both offer pretty strong rewards (suicide belt and special feat for the final floor of utility tower).
I also suspect tattoo guy is mutually exclusive with the charm selling lady, which would imply both offer small bonuses.
I have yet to notice any bonus while using the PSI beetle leg charm. No cost reduction, no extra damage, no extra skill, no extra crit chance or damge according to the offensive sheet. No effect on PSI points, reserves or regeneration either.