Does the remote come with strap to mount it to handlebars?
The amplifier by itself does not, but the ST400 system includes a handlebar mount for the remote.
Can this be used with a SiriusXM radio, and if so, wired or Bluetooth?
Yes, you can connect a SiriusXM unit. Either wired via RCA connection or over Bluetooth.
Can I use it without the remote?
Yes. You can just use your audio device directly, if you prefer.
Is this amp waterproof?
The ST400 Kenwood Motorcycle Amplifier is water-resistant. It can get some moisture but can not be submerged in water.
Will this Amp fit in my Tsukayu Choppa fairing?
The amp is designed to be installed just about anywhere. They fit nicely right above the radio on the stock Harley fairings, so shouldn't be a problem in your Tsukayu. The amp measures '5-11/16 X '1-3/4 X '3-7/8 inch.
Does this have a wired input? Would I be able to connect a 3.5mm cable from my phone to this unit?
Yes, you can use an RCA to 3.5mm cable (included) to connect this amp to your phone or audio device via the headphone jack (3.5mm)