@driftwood714 for starters I recommend wondershare uniconverter.
It's paid, but you can find it in any torrent site like 1337x or rutracker. It has a super easy to use interface, allows you to trim the videos if neccessary, and most importantly it's compatible with a lot of formats.
If you have a modern CPU/GPU you can use HEVC as your desired output format, as HEVC needs less bitrate to achieve a decent image, you can cut the size of your H264 videos in half using HEVC. Just bear in mind that different resolutions will always need more bitrate to preserve the quality.
If you need to reduce sizes too drastically you can also reduce the video resolution.