I ended up going for the banjo brothers, waterproof pannier, in case anyone was curious. I really appreciate all of your recommendations, it really helps narrow the field down.

I ended up going for it because it was waterproof as well as relatively inexpensive ($65). There were some concerns on Amazon about it popping off the back, but so far I haven’t had any issues with this. You could probably fit a small briefcase in it, but it only fits mine when the top is open, which kind of defeats the purpose of the waterproofing, so I’ll probably need to downsize or just move stuff into the bag. It does pretty well for grocery store runs and I haven’t run into any issues with it. I’m balancing the bike or having heel strikes. Certainly not as nice as some of the others that people mentioned on here, but certainly a good starter bag.

I got a Ibera rear rack on Amazon “used very good” for $26. It was perfect, no missing parts. Still some available at this price as of posting. Also got a Rhino Walk pannier on Prime day for $44. Not sure how often they go on sale. I’ve seen them used for backpacking and touring by a lot of people. I’m very happy with it, waterproof, good quality, good finish.

any cheap pannier off amazon is fine for this.

what you want to get is a proper rack that can support 50lbs or so. the rack is way more important than the pannier. too many people get cheap crappy racks and their bags fall off or the rack breaks when they overload it.

you do not need to drop $200 on ortlieb panniers for grocery getting or commuting. those are for touring. wirecutter is for yuppies that have more money than sense, that is their market.

Thank you everyone for your recommendations!

You can get away with one, and I certainly do most of the time. The 2nd one really only gets tossed on the bike for grocery store trips and touring.

Edit: more thoughts

For commuting purposes, it can be nice to get one with organizer pockets, just so keys/wallet aren’t always disappearing all the way to the very bottom