Here is the short, good news:
The official free version of DaVinci Resolve does not add any watermark to your exports. Ever. At any resolution, including 4K, 1080p, or 8K.
DaVinci Resolve’s free version is notable for offering an unusually powerful and professional set of video-editing, color-grading, audio, and visual-effects tools without imposing a watermark on exported projects. For creators who need high-end capabilities without initial cost, this makes Resolve Free an attractive option that bridges the gap between hobbyist tools and industry software.
The free version is remarkably robust for hobbyists and even some professionals:
DaVinci Resolve is unique in the software world. The free version is not a "trial" that expires after 30 days. It is a fully functional editing suite used by professional Hollywood editors.
Advanced temporal and spatial noise reduction for grainy footage.