Whatever you buy, make sure power and ground wire are Oxygen Free Copper (OFC) Wire.
If you want hands off and super plug and play, buy this kit and if you want extra speakers later it will be good for you.
2-/4-Channel Universal Amp Wiring Kit for 1998 and Up Harley-Davidson Touring Motorcycles
Amazon.com: 2-/4-Channel Universal Amp Wiring Kit for 1998 and Up Harley-Davidson Touring Motorcycles: Electronics
www.amazon.com
No cutting required. Otherwise buy, stinger, NVX, kicker, Rockford Fosgate, wires for power and 3-4” RCA’s.
Be sure to run both Power and Ground to the battery, this isn’t like Car Audio. Grounds on the frame of the bike CAN be unstable. You won’t need a radio flash because you are using an aftermarket radio. Depending on which radio harness you buy, you may need something to control hand controls on for the radio. Everything else is pretty simple setup.
If you think later you may want to run lids or speakers in the bag, you can do so now especially if you buy the Stinger kit above, so you don’t have to pull the tank off more than once.
Others will chime in as well, this is a great group here that have done it all!!!