No - crew bonuses do not stack - at all. In the instance two or more of your crew members have an ability that provides a crew bonus, these do not stack. However, there are a few caveats;
Fast Learner (ace) provides a crew experience bonus, this is separate from Fast Learner (not ace) which provides a personal experience bonus. These two bonuses are separate bonuses, meaning if every member of your crew has one point in Fast Learner and one of your crew members has it aced, every crew member will receive a double experience bonus (a personal bonus from having one point in Fast Learner, and a crew bonus from the crew member that has it aced). If two or more crew members have Fast Learner aced, this bonus does not stack.
Endurance (ace) provides a crew stamina bonus, this is separate from Endurance (not ace) which provides a personal stamina bonus. This works in the same way as Fast Learner.
Abilities like Leadership (both ace and not aced) which provide crew bonuses at both levels do not stack. If multiple members of your crew have one of these abilities there is no additional bonus provided to the crew (they will, in the instance of Leadership, receive a 25% bonus for the first tier or a 50% bonus for aced Leadership)
This means, if you're building up a crew that is going to run heists together constantly, you'll want to avoid doubling up on abilities like Leadership but may want to each expend a point in abilities like Endurance or Fast Learner.
The following abilities will affect all weapons:
- Leadership (when Aced)
- Hard Boiled (when Aced)
- Overkill (when Aced)
The Mag Plus skill in tier 6 of the Technician tree increases magazine size for all weapons that do not have a fixed magazine size. This basically means "all weapons" excluding the Bronco (it's a revolver...) and the Mosconi 12G (it's a double barrel shotgun...).
In addition to the above, each class of weapons gets additional bonuses as follows;
Pistols
Pistols are affected by the abilities Equilibrium, Gunslinger, Leadership and (excluding the STRYK 18c) Sharpshooter. The pistols in game are as follows;
- Chimano 88
- Crosskill
- Bronco .44
- Bernetti 9
- STRYK 18c
- Deagle
All pistols are secondary weapons. Pistols fitted with silencers (the Bronco .44 cannot be fitted with a silencer) also pick up bonuses from Silent Killer and The Professional.
Shotguns
Shotguns are affected by the abilities Shot Impact, Shotgun CQB, Hard Boiled, Overkill and Sharpshooter. The shotguns in game are as follows;
- Reinfeld 880
- IZHMA 12G
- Mosconi 12G
- Locomotive 12G
All shotguns except the Locomotive 12G are primary weapons. It is possible to silence all of the shotguns apart from the Mosconi 12G, and doing so will pick up bonuses from Silent Killer and The Professional.
Submachine Guns
Submachine guns get bonuses from SMG Specialist, which can be aced to provide further bonuses. The submachine guns in game are as follows;
- Mark 10
- Compact-5
- Para
- CMP
- Krinkov
- Kobus 90
Submachine guns are secondary weapons. They can also be fitted with silencers allowing them to pick up bonuses from Silent Killer and The Professional.
Assault Rifles
Assault rifles are affected by the abilities Kilmer, Rifleman and Sharpshooter when aced. The M308 rifle is considered a single shot assault rifle due to its semi automatic nature. This means the M308 rifle picks up bonuses from Sharpshooter to reduce spread, in addition to the aced bonus.
The assault rifles in game are as follows;
- AMCAR
- AK
- CAR-4
- UAR
- JP36
- AK .762
- M308
- AK5
- AMR-16
Assault rifles are primary weapons and they can be fitted with silencers, allowing them to pick up bonuses from Silent Killer and The Professional.
Best Answer
At this current time, the other infamy skills have not yet been released. They cannot be unlocked, and no official information about them has been released.
From the official update information: