Welcome to the community.
You can search by clicking on the Magnifying glass icon on the top of the page. This forum the best way to ask questions and look forward answers.
Here’s a guide to getting started with MCEBuddy. MCEBuddy - How to Get Started - User Guides
About file sizes it depends on a lot of things. Three things you can okay with
- Quality slider on the conversion task page - higher the quality, the larger the size and vice versa
- Profile - High quality profiles and slower but create higher quality and smaller files, fast profiles are fast but create larger and lower quality files.
- Codecs - MP4 (h.264) are good at compression, HEVC (h.265) are even better at compression without losing too much quality but are very slow to convert