this one is min 2v , max 4v .. I though it should be ok.
Err no.
You can’t use the RFP50N06 because this takes at least 10V to turn it on. Using it like you are it will get very hot and as you have found will be not very bright.
You need a transistor to boost the output voltage.
See this:- PWM voltage boost for mosfet - Electrical Engineering Stack Exchange
As you see in the video I'm using an Wemos D1,
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