Quark jets look pretty much the same. But there is a way to tag b quarks and to a lesser extent also the c quark. This technique relies on the decay life time of the quark under consideration, which will form a hadronic jet. It turns out that they ( b quark and c quark) can travel a fraction of a millimeter before they can decay. That is there is a secondary vertex, which is not exactly at the collision point where b- bbar pair is created. The place of this secondary vertex can be identified by looking very carefully at the jet. This is the method of b tagging.

A second point is that as the b quark mass is much higher than u,d,c,s quarks, a b quark jet has larger transverse momentum, in the direction perpendicular to propagation direction. So b quark jets are wider.

Efficiency of b tagging depends on the algorithm. Generally it is claimed that efficiency can be up to 70%

Generically, it is very hard to extract information about the Higgs coupling to charm at the LHC. Both charm tagging techniques and searches for h->J/Psi gamma are and will be able to set upper bounds on the Higgs coupling to charm at most at the level of ~few*10 times the Standard Model value. The challenge for the first determination is coming from charm tagging (and more in particular in discriminating between a charm and a bottom jet) and from the relatively small branching ratio of the Higgs into charm. The challenge in the second determination is mainly coming from the tiny branching ratio of the Higgs to J/Psi gamma (few*10^-6).