I'll pass on commenting on running in parallel. I'd be guessing. Contact the manufacturer...very likely one machine badge engineered with multiple different "brands". But the owner's manual will have contact info.
Security: normally I recommend the Kryptonite NY Noose lock. You need an angle grinder to cut thru it...and tests show that you need more than one battery for the angle grinder to get the job done! But at a total of $400 for generators, spending $100 on a lock doesn't make sense. Also, if you don't reinforce the handles, they are the weak point. Add another $50 or more for the handle reinforcements. As they say, fuggedaboudit.
I use a 1/4" chain and conventional Master padlocks (2). With two padlocks, I can get the chain around a large tree and still lock the other end to the genny handle. In the bed of my truck, the chain locks the genny to a stainless u-bolt attached to the body of my aluminum tool box.
This is NOT security. It's deterrence. A determined thief (someone armed with a universal key - bolt cutter - or a decent hacksaw or recip saw) will have the genny in a couple minutes. But it should be enough to encourage most thieves to look for easier prey.
Then there's rain protection and camouflage. A brightly painted genny stands out like a sore thumb. And electrical equipment and rain don't mix well. I use a primitive tent made from a 42 gallon trash bag, a fiberglass driveway marker rod (ridge pole), a couple knob bungees on the genny handle to hold the ridge pole, three tent stakes and a rock - for easy access to the business end of the genny. See photo. Note that the tent allows for excellent ventilation, and the long ridge pole keeps the ends of the tent from drooping over the ends of the genny and the exhaust from melting the tent. I get at least a full season out of one bag.
This jury rig protects the genny in foul weather. Experience during a day-long downpour shows that my genny doesn't like to get soaked. And the bag makes the genny far less obvious to casual observers. The dayglow green cord is another matter.
I setup my 2KW genny at the far end of a 100' 12/3 extension cord if I can to get max noise separation -- my rig was a PUP. The 12/3 cord easily handles 15 amps, and connected to the RV shore-power cord, I had plenty of power for the micro, an espresso machine, and so on. One genny won't run AC, and you don't need it in CO.
Two genny's together need a bigger cover, but my 42 gallon bags - from Ace Hardware - can be cut open to make a longer tent. Don't use a blue "blue-poly" tarp, because it's so obvious, but you can get tarps in camo, dark green or brown. The key is that the tented genny is quite a bit less obvious to someone walking by and perhaps planning a late-night visit to liberate your genny. And they'd be dry in foul weather.
IMPORTANT ADVICE ON CARE AND FEEDING OF YOUR NEW TOYS.
Work them regularly. If you always go where there are hookups, do this at home. Fire them up in parallel, connect them to the rig, and work the hell out of them for 2 or 3 hours. Run the AC, fridge, microwave, and so on. But exercise them about 5 or 6 times a year at minimum. If you let them sit unused, you are likely to get a nasty surprise when you boondock. Small engines don't like to sit - NO engines like to sit. That's why "barn finds" can be very costly investments as used cars.
ALSO: use a DOUBLE-STRENGTH mixture of Sta-Bil in your fuel. If the bottle says 1 ounce, put in 2. Small engines don't like pump gas, but Sta-Bil not only prevents the fuel from gumming up the carb, it also makes it more compatible with small engines. Evidence:
~ my 6-season-old Generac 2 KW generator is on its factory plug. It starts easily and runs very well...despite supporting boondocking camping exclusively AND serving as a backup genny for my home.
~ I have a Stihl 2-stroke gas straight shaft trimmer and a garbage Poulan gas chain saw. Both new in 2009. Factory plugs. Run great.
~ I have a 1998 Honda Foreman ATV with plow. Runs perfectly.
I NEVER drain the float bowls by running them dry. The treated fuel simply does not gum up the carbs...whether I add oil for premix or run regular gas.
Gas can sit in the cans for as much as a year and still run these engines without a hitch.
So exercise your gennies and feed them properly treated fuel. And don't forge to check the oil often and change it annually or more often if you use them a lot.