Why is the RV & its electrical system confusing?

You've got AC and DC voltage and are mixing them up. AC is house power and DC is battery power.

The 50 or 30 amps when referring to the plug in cord is 120 volt AC electricity. What you need to know is your AC appliances can't draw more than 30 amps or you'll pop breakers. One air conditioner can easily pull 20 amps and microwaves pull alot, you'll be close to the max of 30 (2 air conditioners will exceed 30 amps). In your manuals you should be able to find some general specs about what appliances use. You also need to know the max for your generator and avoid exceeding it.

The 45 amps is your 12 volt DC system. The converter converts AC voltage from the cord or the generator to DC voltage. What you need to know there is similar but different situation. The converter will output up to 45 amps with two goals, charge up your batteries and supply your 12 volt appliances. If you exceed the 45 amps then your appliance will continue to operate but you'll be drawing the batteries dead also.

The 50 or 15 choice on the house: You use the 30 to 50 adapter and you have your 30 amp. Now if you use the 15 adapter you are actually creating an overloaded circuit, however it can be used with the proper understanding. The 15 adapter is not safe for the big appliances such as air conditioning, it will however power the converter and charge your batteries. There's plenty more to learn, these are just some basics.

Plug it into the 30 amp service and quit worrying about it. A 45 amp convertor will provide UP TO 45 amps, but if the service is only 30 amps, that is all it will do.

50 amps service is the MAX you can pull, not how much you have to take. the converter cable just allows you to hook into smaller plugs, if that is the option.