Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
For plants only you could get by with a much smaller filter, just enough to keep a little water moving. There will be very little in the water to filter out, no major nitrogen cycle, so I think I would use at least a small powerhead to keep a bit of water moving, maybe a sponge over the intake.
Yes, omit the heater. Most aquatic plants are fine at reasonable room temperature.
If there is good sunlight, you might omit the light, but if you are where there are either a lot of cloudy days or such hot bright days you want to close the curtains then you would need the light.
Frogbits is another pretty easy floater.