Personally I use a Benro IB2 ball head on a Leofoto 328 https://amzn.to/2NHDb4T
Holds fine, and works great as a spotter setup. No the most stable setup (espically compared to a RRS tripod + anvil 30) but works for me for now.
Amazon.com : Neewer Professional Metal 360 Degree Rotating Panoramic Ball Head with 1/4 inch Quick Release Plate and Bubble Level, up to 17.6pounds/8kilograms, for Tripod, Monopod, Slider, DSLR Camera, Camcorder : Camera & Photo
Amazon.com : Neewer Professional Metal 360 Degree Rotating Panoramic Ball Head with 1/4 inch Quick Release Plate and Bubble Level, up to 17.6pounds/8kilograms, for Tripod, Monopod, Slider, DSLR Camera, Camcorder : Camera & Photo
Really depends on what your doing, and how stable you want it to be. Personally I would not trust my fairly expensive rifle on a $20 ball head (nor my expensive cameras).
You don't need an RRS head but I would spend a little more then $20.
What about recommendation for just a an ARCA plate. I could just install a plate onto my existing shoe on one of the 2 normal heads I already have for my tripod.