What other firms are there besides MBB and how does do they compare to MBB?

In consulting there is a group of firms right under MBB, but above the rest, that is commonly referred to as the Tier 2 consulting firms. The list of what's considered Tier 2 can vary based on region and industry, but in the US the most prevalent consulting firms are, in no particular order:

Oliver Wyman, Strategy&, EY-Parthenon, LEK, Kearney

These are the firms that are closest to MBB in terms of breadth and quality of strategy work. On average, they are substantially weaker than MBB, but each has at least a few industries where they compete regularly with or even beat out MBB. They also pay similarly to MBB, and some (LEK, S&) pay even more than MBB after certain levels

Then you have the industry or practice-specific consulting firms, which include:

AlixPartners, Alvarez & Marsal, ZS, Altman Solon, etc.

AlixPartners and A&M specialize in restructuring consulting, and as their pay/bonus is largely utilization-based, compensation numbers can often look more like IB than consulting (needless to say, much higher than MBB). ZS and Altman Solon pay more similarly to what other T2 firms pay, and have industry specializations (Healthcare and TMT work, respectively).

Then you have the management consulting arms of the Big 4 and Accenture, namely:

Deloitte, PwC, KPMG, EY, Accenture S&C

These will do less, if at all, strategy consulting work and will mostly be implementation-focused. They also pay significantly less that MBB at almost all non-entry levels, and career progression is slower here than at all the other firms listed above.