You should be fine. Rhinos don't have a huge charging system but I see plenty of them all the time with more than just a light bar. If you are going to be leaving it on for a long time, a larger battery would probably be a good idea. The average dual row 20" light bar is ~120 watts (or~10 amps). A relay would also be a good idea, but most good rocker switches are rated for 20 amps so they would handle the load just fine. Be sure to fuse the hot wire close to the battery.
For brands, I honestly see no point in buying the high dollar Rigids or Vision X, etc. They are mostly Chinese components that roll off the same assembly lines as some "knockoff" Chinese brands like Totron. Some of the high end ones are assembled in USA and have a good warranty, but you can buy 4 of the better Chinese light bars for the cost of one of those. Totrons have a pretty big following and some of the vendors will give you a long warranty. Light It Up Offroad is a good dealer, as is WV Offroad.