Don't know much about either city, but La Chutes de la Chaudieres is a nice place to stop for an hour or two.
We did notice a few years ago that free overnight parking in Walmarts out in the Gaspe has been reduced to only being allowed (by warning signs) from 23:00 to 06:00, since around 2017. Not sure about the ones closer to the St. Lawrence River. Used to be wide open in Quebec, but the increasing extensive (ab)use of their parking lots as free campgrounds brought on the all day parking bans, I guess. The roadside parkettes and pull outs were also wide open, but now are signed "no overnight parking/camping", as well.
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)