I have a Wittner MT60. I love having a physical metronome and I can select it to have a constant beep or have a different sound play on the first beat of the measure.
https://www.amazon.com/Wittner-MT60-Pendulum-Metronome-Display/dp/B000EENFPE
Mine was a gift and I think it was priced less than these on Amazon.
One thing about a metronome, start out by playing a song at half speed or slower. For example. if the song is at 100 BPM's start by playing it at 50 BPM's and then progress to a faster tempo once you can finger it well.
i would suggest using a metronome for all playing styles. Strumming off beat is just as bad a noting off beat.