so i should use High Quality Portable vbr instead of 128
Absolutely. You can expect the overall average bitrate to be about 130-140 kbps for modern loud pop/rock music and 115-130 kbps for classical, "quiet jazz", acoustic folk, etc. Naturally individual files may vary more.
Also, if you must re-encode (aka transcode) you should avoid transcoding files that are below about 200 kbps (if you care about audio quality). This is of course just my opinion, but I follow that rule when I "must" create smaller files for a portable. Naturally you can convert a bunch of various test files (perhaps of different genres) and judge the quality by yourself.
Do I need to copy all the files to another drive so that I may keep the orginals
In any case that would be a good precaution if don't already have a backup archive of the files.