There's a number of effects that he has permanently built into his body, namely easily hideable or internal capabilities
Capsules come in lesser and greater ranks, but due to their design, have a time limit before the serum burns out and the change reverses on it's own, currently, ranging between 30 seconds and 5 minutes.
Lesser capsules contain a lesser change, such as sprouting wings, or claws only.
Greater Capsules, contain some sort of powerful Combination of changes, but tend to burn out faster than lesser capsules.
Essentially, they function as sudden changes to compensate for mistakes of vulnerabilities, though short-term [for balancing purposes obviously XD], and sometimes painful.
Injectors are his main form of genetic transformation, causing complete and permanent changes to his body by pouring a serum into his blood-stream that bonds his DNA to that of other creatures, aka, Gene Splicing.
He can currently only combine 2 at once, though prefers to stick to just one when possible, because 2 strains his body as he has yet to progress his skill and knowledge to make more safe to combine.
These changes are permanent, though they don't change his mind itself, physically borne instincts and the like still come into being for him. He also keeps a number of other Injectors handy that will Turn him human again.
An Injector based transformation, being so complex, thorough, and permanent, takes a little time to complete, but bring greater long-term effects than things such as capsules.
Gasses come in a small ball capsule form usually, and contain a combination of powders and chemicals that mix to create a gaseous cloud on release and create some sort of effect on those caught inside.
These effects do not 'transform' their recipients, though he may come up with something capable of such in the future, they currently only create certain internal effects on those affected by the gas, which can often be either inhaled or absorbed through skin contact, or affect things in some other way, the specifics will be detailed when revealed.
These effects may range from sapping the strength from a victims muscles, essentially forced fatigue, to pepper-spray like effects, or even creating things like oils or pasty muck.
However, they may also have beneficial effects he can provide to allies, such as re-energizing, aiding in natural regeneration, or an adrenaline boost, and so on.
These effects obviously are temporary, except for very few special ones, and will generally only last up to a minute or 2 currently.
Thus far, no potentially fatal effects have been planned.