my tent is 5ft and i use a 600w.
600w HID lights generally need 18-24 inches of space depending how well they are cooled. if you take into consideration that and your space taken up by soil pots or hydro equipment (usually around 1 foot)
that makes 3 feet of dead space you don't want to enter.
burnt tops are super
200cm is 6.5 feet so you should be plenty good for most plants excluding a pure sativa.
A 600w should elminate any stretching that would occur with a insufficent amount of lumens my MH puts out 58,000 and my HPS puts out 100,000 lumens. plenty for a 100cm floor space. 600w bulbs can grow a 4ft by 4ft area well.
Hope this helps