Have you tried H265 yet? If you're seeing 70GB with H264, you should get about 60% of that file size (so, 43GB); however, even thought it's a MP4 it won't play back on as many devices as H264 as H265 is not a standard yet. Also, it's a little tricky to find in Adobe Media Encoder because the Format appears as "HEVC (H265)".
If rendering to QuickTime movie file format, Apple ProRes 422 {Proxy) yields a relatively small file with good image quality.
What is the intentended use for you rendered movies? Broadcast? Social Media? Mobile devices? More othen than not, the delivery format determines your settings and your files sizes are in keeping with those settings.
For what it's worth, H264 is one of three compression types still supported by Apple for both compression and decompression. It just hasn't been through QuickTime since 2013. While the MOV file format is still in use, it's AV Foundation Frameworks now.
-Warren