Question about Lighting

Good afternoon, we are now planning our light fixtures and I have some questions. The robots on most websites where you buy these things do not seem to know what I am talking about so hope someone here can help.
We have a house built around 1905 in which we found gas pipes n the ceiling. I believe the house had electricity and gas when it was built and I am looking for period appropriate light fixtures.

The ceilings are not that high: about 8-1/2 feet, 9 in others. I would have 30 inches at most from ceiling to bottom of the fixture.

I am looking at some typical Victorian gas/electric chandeliers which have etched glass shades attached to curving brass arms. Please tell me how many arms, or “shades” the lamp should have for a space about 14 feet s square. in order to give us adequate lighting. Each of the glass shades on the fixture can accommodate a 60 watt bulb. If there were four shades it would emit 240 watts of light.

Is there some kind of formula or ratio to use when calculating how many watts of light you will need for a given space?

There are shades that point up for gas and some that point down for electric. For the gas shades, how far down from the ceiling would they have to hang ? Each of the gas lamps in the fixture would have held a live gas flame. I am not worried about my ceiling but I do not want the fixture to look too short.

Thanks in advance and looking forward to some good advice here.