General case: your utility sets the requirements for this
Since the meter socket is part of the interface between you and your electric utility, most electric utilities publish a document that specifies what sort of meter socket they want, among the other various requirements and conditions they place on consumers of electric services. For the case of PG&E, this document is called the Greenbook.
In your specific situation...
PG&E is a member of what's called EUSERC -- this is a coalition of utilities that set and use a common standard for metering equipment. In particular, you will need a ring type meter main that conforms to the EUSERC specifications (EUSERC drawing 301, 301A, or 302, to be precise, but if the manufacturer's catalog says that it complies with EUSERC, that's good enough). As a result, the QC3040M200S is not usable for you; in fact, none of the Class 200 (150/200/225A) all-in-one CSEDs in the QO line meet EUSERC requirements, so they're a non-starter for you.
Furthermore, PG&E will not accept a setup with the meter for a single-family residence inside a garage -- this is prohibited by the Greenbook, section 5.3.2, point F. So, you'll have to put the meter-main and any loadcenters on the outside of the garage instead if possible (as you can't put the subpanel by the gas meter either, NEC 110.26A would likely prohibit it even if the Greenbook didn't). Thankfully, this gets them out of the way of the gas meter set, so you now have the flexibility to use a separate meter-main and loadcenter, as described below.
If this doesn't work, then you'll have to find a new home inside for the setup, or hope that PG&E and your electrical inspector will grandfather the noncompliant location.
Avoiding repeating this pickle down the road
One of the problems with "all-in-one" service entrance devices, as you are finding out the hard way, is that they tend to be short on breaker spaces and are hard to expand or replace. As a result, if a meter-main is required, the use of a single-disconnect meter-main or a meter-loadcenter with feed-through lugs in conjunction with a separate 200A panel is a far better choice than a single 200A meter-loadcenter combination from an expansion and flexibility perspective.
Given the lack of options in the QO lineup for this, I would go with a Siemens MC0816B1200E(FN/FT/SN) for the meter main. It is listed as EUSERC approved in the Siemens catalog, has 8 full size spaces for outdoor branch circuits or the like as well as an available secondary main disconnect of up to 50A (useful for an outbuilding), and has a set of feed-through lugs at the bottom of the busbars that can be used to provide the full 200A capacity of the main breaker to a subpanel without taking up any spaces. With this, you can use a 200A panel of your choosing -- I would use something with a minimum of 42 spaces, but would not turn down a 54 or 60 space unit if one was available. Plug-on Neutral is a nice-to-have (albeit not necessary), and since the meter-main provides the main disconnect, you can use a main lug panel for the subpanel.
Sidebar: 4-jaw vs 5-jaw
Self-contained electric meters and meter bases/sockets are not all alike -- they come in various current ratings (or Classes), as well as in various jaw configurations to accommodate different supply systems. The 120/240V split-phase system used for most houses and light commercial buildings uses a 4-jaw meter and socket, as it only needs to be involved with the two hot lines (hot 1 in, hot 1 out, hot 2 in, hot 2 out).
A 5-jaw meter socket and matching meter are used when the service is a "2 out of 3" service, where instead of providing 2 legs 180deg apart from the opposite ends of the supply transformer, you get 2 legs and a neutral 120 degrees (and 208VAC) apart, as they came from picking 2 legs out of the 3 phases provided by a 120/208Y connected three phase supply. Many 4-jaw sockets can be converted to a 5-jaw configuration in the field using a fifth jaw kit, as all this fifth jaw does is supply a neutral connection to the meter so it can correctly measure power in this asymmetric configuration. However, unless you are in NYC (and you aren't), you will only see a 120/208 3-wire service or feed in a high-rise building fed by three-phase electricity.
So, while a 5-jaw socket can be used in a 4-jaw application (with the neutral jaw sitting unused), 4-jaw sockets are more widely available, so that's what I have specified here.
