IMO 400l/r may be too much, it's certainly not needed and may be too much.
consider if you have a bucket that's 20l in size, and you use it to gravel vac the old fashioned way. you siphon water out of the tank into the bucket and it takes 10 mins to fill.
that's a flow rate of ~120l/h, so less than 1/3 of what you're suggesting you'd use... obviously numbers are based on guesses and can be determined by the equipment you're using and the drop to the bucket.
you can get other devices that are air and battery powered to do the same thing, they work and don't move anywhere near as much water.
the higher the flow, the more chance you will have of moving substrate, uprooting plants, sucking in fish... so the lower flow you use, the easier it will be in your tank. If you have the option of a dc powerhead, use that so you can change the flow rate to suit your needs.