Not only is it possible, 27 GB is quite reasonable. For reference, an uncompressed 1080p video that is 1 hour long will be around 500-600 GB. Any movements you make towards lower file size will adversely affect the quality of your export. For the best balance, you might want to export to HEVC (H.265), and turn up the quality settings. While this offers the best picture quality at low file sizes, be warned that this is a very computationally-expensive format, and exporting will be very slow, especially for a 1-hour long video. Also, since this is a relatively new format, it has limited or no support on many devices, and you might not be able to upload it to some sites, including YouTube. A reasonable compromise might be to use H.264, use Variable Bit Rate (VBR), and keep your bit rate range around 2000-3000 Kbps. The lower you go with your bit rate, the worse your picture will look, but you will end up with a smaller file size. I should add that in the Export Settings window, Premiere gives you an estimated file size when you use H.264 or H.265. Use that as a guide and tweak your parameters accordingly.
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