It doesn't matter in the slightest how bright (or not bright) the LEDs are that you use, unless the lamp is designed to be used with your headlight assembly it is illegal.
I won't make the mistake of assuming the motive of others for posting in this thread, I only speak for myself ... recommending that someone use an unapproved headlight set up is illegal and most importantly dangerous. Years ago I spent a considerable amount of time researching this topic because I wanted to upgrade the headlights on my old work van. Before I started looking into it, I had no idea it was possible to buy aftermarket bulbs that were not legal to use on the road. I found
CPF (CandlePowerForums) to be extremely helpful in this regard ... I highly recommend you browse through, especially the "Vehicle Lighting Laws & Regulations • Documents & Links" sticky created by Virgil.
My only interest here is to share information. As always, people must needs make there own decisions based on the information that they have ...
As far as the headlights on my old van, a number of people recommended Sylvania SilverStar ULTRA and I was really happy with them.
Here is a link to the offerings they have for a 2011 Mazda 3 (High Beam).
Dan