I don't know about the CharBroil, but I converted my Members Mark to NG a year ago by drilling the orifaces for the main burners to 5/64's and the back burner to 1/16th -- this may at least get you started in the correct direction. When you convert to NG you do not need a regulator. One less thing to go out. ;->

No. Shutting it off with the shutoff won't do anything different than turning off the gas at the burners. Only thing to watch is that the shutoff is mounted securely enough to take the abuse of repeated use. Some I've seen are pretty flimsily installed.

A lot depends on the level of the grill from FM. I had one for almost 10 years and it was a great grill. Replaced it with Lynx. Great grill but many replaced parts. Building new and going back to FM Echelon 790i A. I dont like the E because its just another thing to break and not worth the extra money. These grills get extremely hot. I cannot hold my hand over the grids if it has been on high with the lid closed. There will be no comparison to your Weber. It will blow it away. Keep in mind with warranties, they will usually replace all parts but you are responsible for shipping and installation. Also, I have never met an igniter on any grill that lasts more than a year or two, so be prepared to manually light in the future.

Let's straighten out the terminology. There are charcoal BBQs, propane grills, electric grills (which tend to be quite small because they're limited to 110V - 15 amp, not enough to power much more than a small coil). Just like broilers, gas models have an open flame that's usually partially shielded and electric models have heating coils that turn red. Electric broilers in ovens and ranges are usually connected to beefed up 220V circuits and can have larger and hotter coils than small portable electric grills. I have gas and electric broilers and gas and charcoal BBQs and my experience is - cooked food that browns (the Maillard reaction) develops more pleasing and interesting flavors. Any cooking device will do that when hot enough. Electric and gas broilers are about the same, gas ones produce less odor when vented by a cooking exhaust system (as mine is). Propane grills are quick and convenient to use. My experience also is that the price paid for having the convenience is that the cooking results are inferior to using a charcoal BBQ, in terms of flavor and heat placement alternatives. I can do things on my Weber charcoal BBQ that I still struggle to do on my gas grill. Maybe it's because of having more charcoal experience. Flavor outcome, no contest. Using a gas grill is like using a broiler. Nothing wrong with that and I use our broilers often, but propane grills just don't produce the BBQ flavor people expect from outdoor cooking. The downside of a charcoal BBQ is that they're a bit messy and take time to get going but I find it worth it when I can plan to use it. Using the charcoal model can't be a spur of the moment decision when hungry, while using a broiler or a propane grill can be.