These are not character classes. BBR doesn't do character classes. This is an overarching view of what kind of sapient life one may encounter (or portray) in the wasteland.
Let us define our terms.
Baseline - this is and generally looks like (make-up and fashion choices notwithstanding) your average human being, no enhancements or dramatic mutations. Just the tireless persistence hunter-terminators natural selection created over millions of years of the most unforgiving field-testing the planet has to offer, no big.
Mutant - we readily accept and own that there is no such thing as advanced living organisms that aren't mutants on some level. However, for our intents and purposes "mutant" means "someone who is visually different from what one would expect to see in the average baseline". We only count people with visible physical mutations as mutants, because otherwise what's the point? It's worth pointing out that being a mutant carries no social stigma in the world. Being a mutant is considered normal, having a problem with mutants generally is not. There are exceptions to this, of course.
Transhuman - or post-human, depending on personal preference. May at one point have been baselines, but are no longer recognizably so. These are your cyborgs, improved clones, genetic experiments, nano-tech enhanced agents and super soldiers of tomorrow. Brain2brain interfaces, living data repositories, wet-ware hackers and old-world tech junkies. All manner of cyberpunks welcome.
Machine - constructs through and through. Robots, androids, mechanical spiders and other creatures with artificial or simulated intelligence and reasoning skills. AIs (smart and otherwise) and expert systems file here. Does this unit have a soul? Probably.
We recognise that dressing up for certain kinds of characters is more work than for others. To reward the hard-working mutants and transhumans (and machines) among us, we've come up with some rule-based perks.
Please note that our perks are based on our existing rules. We're not going to make any additional rules but if you have a fantastic idea of something special your mutant/transhuman can do please email us and we'll talk about it: firstname.lastname@example.org
Also note that all perks are 100% optional. If you want your character to be a mutant cyborg purely for cosmetic reasons we encourage and salute you.
This is the list of rule-oriented advantages. You are limited to two of these:
Shock Absorbent Braincase - It is impossible to Knock (2.11) you out.
Enhanced Metabolism - Ingested drugs, narcotics and poisons only have as much of an effect on you as you want it to. This applies to alcohol as well.
Tough - You have an extra hit point. (You can take this perk twice for two hit points.)
Improved Regeneration - Cut your natural (30 minutes) healing time in half with this perk! 15 minute healing.