DPReview added the Panasonic S1 and S1R to their studio scene comparison tool today. The S1 and S1R seem to compare well to the Sony a7 and Sony a7RIII. If you want to more closely compare Panasonic’s new cameras you can do so here.
Panasonic S1: B&H Photo / Amazon / Adorama
Panasonic S1R: B&H Photo / Amazon / Adorama
Sony a7III: B&H Photo / Amazon / Adorama
Sony a7RIII: B&H Photo / Amazon / Adorama