New INT 650 Owner in Coastal GA - What oil works best?

Hello all,
Recently bought my Royal Enfield and the first oil change and maintenance cycle is close. I have never used anything thinner than 20w oil (used to Yamalube). Are there pros or cons to running thicker oil (since it gets pretty hot here during the riding season) or should I follow the manual? Also, apart from inspecting hoses and controls, changing oil, and checking the valves, is there anything I should pay special attention to?

Thanks so much!
-Bliss