Flame King is Chinese made and kissing cousin or closer, to the Winntec 6020 which is a huge fire hazard (and was recalled)
Best choice is the Marshall Excelsior MEGR253. Models with an L suffix are lower flow rates, have blue paint on the large diaphragm housing and at 150K BTU flow are quite OK for almost any RV. Models with no suffix and no paint on the housing are 225K BTU and also can be used on any RV. The suffix H models have OD green paint and are high flow, 350K BTU and the extra capacity is not really needed. If there is a P suffix it simply means it is in a clear plastic hard shell package. Without the P it is in a plastic bag and came to the seller in bulk, more prone to being damaged.
You also need the plastic cover that covers the vent to protect the vent. Required by the DOT. https://www.amazon.com/dp/B00KTS0WOC?th=1
Pages 7-9 of this ME camping catalog will tell you all about the regulators and how they operate. Marshall Excelsior Camp and RV catalog
Fairview regulators are made in Mexico and have reliability issues.
Cavagna Kosan regulators are made in China but of Italian design and in company owned plants, and seem to be of decent quality. https://www.amazon.com/Cavagna-Kosan.../dp/B07BCK2JNM