Can you use a 450 watt white led light to start se...

Yeah - you don't want to transplant autos EVER... they just don't like it at all. I generally have my lights about 30" above my seedlings because I grow in a tent but I have friends who have a grow ROOM and they put their lights about 5' above... You just don't want to get them too close because they will easily burn. Putting them up high also encourages stretch. Beyond that, it's a matter of "reading" your grow to see what they need... if they look like they're too tall and spindly, lower the lights... if they look "normal," don't move the lights... if they're stacking up and too bushy/not enough space between nodes, move the light higher... They really WILL tell you what they need/want! Good luck!