Early 80's Japanese mid level bikes like bike like Nishiki, Centurion, panasonic, bridgestone, univega get my vote you can keep them simple (friction or upgrade) easy to work on and good quality

easy to put a north style bar on for more upright commuting (and then use a thumb shifter)

both of these wold work, the bridgestone is a upper end model

and to be clear Steel frames are not heavier than aluminum

63 cm in bellingham $125 https://bellingham.craigslist.org/bi...945112402.html

loooks like a nice bridgestone $325 https://seattle.craigslist.org/see/b...953742405.html