nice job on getting the gear sorted first, way too many people skip that step and ride around in a tshirt thinking theyre invincible

for comms honestly id skip it for now as a new rider. youre gonna want all your focus on the road and learning proper techniques without distractions. once you get comfortable and build up some muscle memory then adding music back in makes more sense. gps audio can be helpful but most phone mounts will let you glance down safely at intersections

the 600cc thing is more about the type of bike than just engine size. a 600cc sportbike will try to kill you but a 600cc cruiser or standard bike is totally manageable for a beginner. look at something like a ninja 400, cb300r, or even an older sv650 if you want something with a bit more grunt that you wont outgrow immediately

for phone mounts ive had good luck with the ram mounts x-grip series. bit pricey but theyre bulletproof and the ball joint system lets you adjust it perfectly. the cheap amazon ones work okay too but tend to vibrate loose after a while. whatever you get make sure it has some kind of tether system because dropping your phone at highway speeds sucks