I'll try and answer some of your questions as best I can:
- 5 L at 200 bar would give you an approximate 5*200 = 1000 liters of unpressurised gas. With a flow rate of 15L per minute you would have 1000 / 15 = 66.67 mins of gas flow. Peaceful Pill handbook advises a 25 mins of gas flow, which would make a 5L cylinder at 200 bar more than enough
- A regulator lowers the pressure - the gas in your cylinder is highly pressurised and just opening it without a regulator would be a bad idea. Your regulator gauge indicates the pressure of your cylinder - when connecting, check if it is at 200 bar as it should be (in the case of a full cylinder)
- A flow meter allows you to control the flow of gas from your cylinder in liters per minute so you can more accurately control the flow of gas, Peaceful Pill handbook advises a flow of 15L/min for our purposes
- I'd advise you to purchase a
combined regulator and flow meter as in your second post with pictures - less parts, less chance of wrong connections
- Please check the valve connection on your cylinder to know what regulator w/ flow meter you need.
- For the hose a PVC hose would be preferable to an inert gas hose: it's more flexible, lighter and if you have the right diameter just as good / airtight. I personally use a silicone hose that is even more flexible and can be stretched out to fit the exit valve using a bit of hot water to soften it up
- Your gas will be exiting your cylinder at 1 bar (normal atmospheric pressure) so you don't need to be concerned about the pressure your hose can take - the inert gas hoses you posted are designed to handle high pressure which we don't need in our case